The four presentation modes of a PDF

Understanding the four presentation modes of a PDF is essential to getting the best-quality export from your authoring program. In this article, we’ll explain the four modes and how they relate to each other, particularly in the critical and sometimes complex matter of reading order.

The four presentation modes are:

  • Layout view
  • Reflow view
  • Tags mode
  • Read Out Loud mode

These modes are primarily described as they operate in Adobe Reader and Adobe Acrobat. However, it’s important to understand that other PDF readers with specialised assistive functions will be superior in some of these modes than the Adobe PDF programs, and while Adobe Acrobat Professional is indispensable in the production of tagged PDFs, it is quite limited in the presentation of those tags.

Layout view

Layout view displays a page-based layout equivalent to a printed page.

Assistive functions available in layout view are:

  • options to override the existing colour scheme with a choice of high-contrast colour schemes
  • the ability to zoom into and pan around a page
  • the ability to view alt text on hover.

A characteristic of layout view is that if the layout is complex, there is no objectively defined reading order. Each reader will navigate the content based on their subjective interpretation of the layout.

Reflow view

Reflow view displays the page content as a single flow of text and objects, even if the layout is multi-column or is complex in other ways.

Assistive functions and characteristics of reflow view are:

  • options to override the existing colour scheme with a choice of high-contrast colour schemes
  • automatic reflow of the document content within the width of the document window, thereby averting the need for horizontal scrolling at high magnifications
  • the ability to view alt text on hover
  • convenience on smaller mobile devices
  • removal of non-essential text and graphics (artefacts)
  • unambiguous reading order.

Adobe’s reflow view is not based on the tags, but on the page formatting. Headings are distinguished by whatever formatting mechanisms are used in the layout view, for example font size, weight, variant, colour.

By comparison the specialised (and free) VIP PDF-Reader does not display the layout view at all, but only displays a reflow view based on the tags. This means it can identify headings and format them in a manner suitable for low vision users. The current first version of  VIP uses large spreads in font sizes to make it easy for readers to visually identify the level of heading. A future version might enhance this feature by offering users the option to control the formatting of headings, for example by using different colours.

Another free specialised reader, pdfGoHTML, offers similar capabilities as VIP, but in addition it allows users to see the document structure elements and tags alongside the text. This feature is particularly useful for users who find it difficult to rely on visual formatting to interpret the role of a paragraph or other element. Unlike VIP, pdfGoHTML cannot open a PDF directly – it can only do so via Adobe Acrobat (which is not free).

Tags mode

Tags mode is not a ‘view’ as such but a structure for presenting the document in the user’s preferred format, which could be visual, aural or tactile. For example, the tags in a PDF can be read by a screen reader, which will either voice the content (and structural information) to the user, or pass the content and structural information to a braille machine.

Assistive functions and characteristics of tags mode are:

  • can be read and navigated by screen readers
  • can be reflowed by specialised visual readers that allow users more control of the presentation, including the explicit display of tags
  • document structure and alt text can be programatically determined (that is, assistive software can discern structure and alt text and announce it to the user – this is not possible in either of the visual views or in Read Out Loud mode)
  • unambiguous reading order.

Read Out Loud mode

Read Out Loud is a (very) basic screen reader built into Adobe Reader and Adobe Acrobat.

Assistive functions and characteristics of read out loud mode are:

  • reads tagged content, in the order of the tags
  • if there are no tags, it infers reading order, which will generally match the reflow view reading order
  • pauses to indicate a new paragraph
  • does not announce any other structural information
  • unambiguous reading order.

What you need to know when exporting from InDesign

Layout view

Easy  – what you see in InDesign is what you get in the PDF. However, that doesn’t mean the layout will be correct for the other three other modes. So even if the objects look right, it doesn’t mean they are right – they may still need considerable tweaking.

Reflow view

The principal objective for exporting to reflow view is to set up the correct reading order. This is controlled in the Layers panel.

Each text frame and graphics frame on a page or spread is shown as a separate item in the Layers panel. The order of the items shown in the Layers panel in InDesign is highest object first to lowest object last. Reflow view in Adobe Reader and Adobe Acrobat displays the content within these objects in the opposite order, that is, the content in InDesign’s lowest object is displayed first and the content in InDesign’s highest object is displayed last. While this may seem illogical, the logic is that by default the lowest object on a page is the one created first, and therefore represents ‘earlier’ content.

If the order you see in the Layers panel does not correspond to the correct reading order, drag the items in the panel to the desired position.

Keep in mind that when an InDesign layout is set up as two-page spreads, the Articles panel shows the layering order over the entire spread. However, Acrobat’s reflow view shows content one page at a time, so for each page it will pick out the relative order of just the objects on that page. A good approach in InDesign is to have all the objects on the left page below the lowest object on the right page, and within each page have the objects in the correct order.

The Layers panel will include objects that have been designated as artefacts. These will not display in Acrobat’s reflow view. If possible, put all the artefacts lowest in the layering order so they don’t distract you from dealing with the other objects.

Note when exporting a PDF from InDesign that although the reading order of reflow view is not based on the tags, the reflow view may not be coherent and in the expected reading order if you export an untagged PDF rather than a tagged PDF. The tags include some essential information that reflow view depends on.

Tags mode

The objectives for correct export to tags mode are to:

  • export all substantive content in the correct reading order
  • apply and export the required structure tags and alt text
  • exclude non-essential text and graphics (artefacts).

The reading order for tags mode is controlled in the Articles panel. This means that the reading order for reflow view and the reading order for tags are controlled by two different mechanisms. The key points to understand are:

  • there is no mechanism for synchronising the two orders – they each have to be set up independently of each other
  • the order for the purposes of reflow view applies on a page-by-page basis, whereas the order for the purposes of tags applies on a whole-of-document basis (e.g. it is possible to have content on the last page appear first in the tags)
  • the elements that are ordered in the Layers panel are graphics and individual text frames, whereas the elements that are ordered in the Articles panel are graphics frames and entire stories (even if they span multiple pages)
  • To ensure that InDesign exports tags based on the setup in the Articles panel, check ‘Use for reading order in tagged PDF’ in the Articles panel menu.

How to apply structure tags, alt text and artefacts is a whole other topic, which we’ll discuss in a future article.

Read Out Loud mode

As explained above, Read Out Loud mode by default draws on information held in the tags of a PDF. There is no special setup required in InDesign to ensure correct export to this mode.

What you need to know when exporting from MS Word

Layout view

As with InDesign, what you see in MS Word is what you get in the PDF. However, that doesn’t mean the layout will be correct for the three other modes, especially if you have used floating text boxes and picture boxes. So even if the objects look right, it doesn’t mean they are right – they may still need some tweaks.

Reflow view

The principal objective exporting for for reflow view is to set up the correct reading order in MS Word. If your document is laid out as a single text flow, and you have not used floating text boxes, picture boxes or tables, then you probably have nothing to worry about here – reflow view will display the content in the same order as the MS Word document. This will be the case even if you have used the Columns feature to set up multi-column pages.

It is not a good idea to use floating content if you want to create an accessible PDF from an MS Word file, as you do not have total control over how it will export. If the use of floating content can’t be avoided, you may need to do some test exports to see where your content ends up in the reading order, and you may need to accept some compromises. For example, in reflow view:

  • anchored boxes layered behind the text will appear at the top of the page, before the main text flow
  • anchored boxes layered in front of the text as well as inline boxes will appear at the bottom of the page, after the main text flow.

In both scenarios the boxes will ‘interrupt’ a paragraph that runs over two pages, so these paragraphs should be repositioned onto a single page.

Tags mode

As for InDesign, the objectives for exporting to tags mode are to:

  • export all substantive content in the correct reading order
  • apply and export the required structure tags and alt text
  • exclude non-essential text and graphics (artefacts).

In this article, we’ll just consider the issue of reading order. We’ll deal with the other aspects of setting up for tags in a future article.

As for reflow view, if your document is laid out as a single text flow, and you have not used floating text boxes, picture boxes or tables, tags mode will present the content in the same order as the MS Word document.

As we said above, it is not a good idea to use floating content if you want to create an accessible PDF from an MS Word file. If you have to use floating content, you will have to check the resulting tags in addition to checking reflow view. Note that the two orders will generally not match – MS Word uses different paradigms to export to each of these presentation modes.

The good news is that MS Word does a better job of exporting floating boxes to tags than it does to reflow view. For example:

  • inline boxes will be read in the correct order
  • anchored boxes layered behind the text will be read before the paragraph to which it is anchored
  • anchored boxes layered in front of the text will be read after the paragraph to which it is anchored.

Read Out Loud mode

As in InDesign, there is no special setup required to ensure correct export to this mode. Read Out Loud mode simply draws on information held in the tags of a PDF.

What you need to know when checking a PDF

Layout view

  • Do not assume that the order you see in the layout view is the same as the reading order in the other two presentation modes.

Reflow view

  • The accessibility checker only checks the tags, therefore it cannot pick up any problems in reflow view
  • It is advisable to check the reading order directly in reflow view as well as via the touchup reading order tool
  • Reflow view does not display artefacted backgrounds, so white text will be invisible – in order to see it, go to accessibility preferences and set the colour display to black on white or another high-contrast mode
  • While the touchup reading order tool can be used to repair reading order, it is quirky and unreliable and can make content disappear, and there is no unsave when using it. The cause of incorrect reading order is faulty setup of the source document, so it is generally better to repair the problem in the authoring program and re-export the document.

Tags mode

  • The accessibility checker cannot check:
    • whether the reading order of the tags is correct
    • whether structure tags have been correctly applied and exported
    • whether artefacts has been correctly designated
  • The touchup reading order tool does not change the reading order of the tags – it only changes the reading order in reflow view, and, as stated above, it is preferable to repair reading order for reflow view in the authoring program
  • To check the reading order of tags against layout view, expand tags as necessary and move down through the tags using the down arrow on your keyboard. As each tag is selected the corresponding content in the layout is highlighted
  • If pages are inserted or added to a PDF, the incoming tags will generally not import into the correct reading order, so they will need to be re-arranged in the Tags panel
  • When tags are edited or re-ordered, the adjustments generally have no effect on layout view or reflow view (such actions are sometimes necessary to enhance accessibility, for example a footnote can be repositioned in the tags order so it is read immediately after the end of the paragraph containing the footnote marker – in layout view and reflow view they can easily be located at the bottom of the page, but in tags mode there is no such thing as the bottom of a page)
  • If the authoring program has not exported tags, and the document is published without tags, then a user opening the PDF with a screen reader will experience a delay while Adobe Reader generates tags as best it can. The screen reader then reads those temporary tags. They may or may not be in correct reader order and they will typically include minimal structural information.
  • If you have an old PDF without tags and the source document is no longer available, it is possible to manually add tags in Adobe Acrobat, but this is time-consuming for a document of any length.

Read Out Loud mode

  • Read Out Loud is a basic screen reader. If the tags in a PDF are correctly set up, then Read Out Loud will automatically work to the maximum of its limited capabilities – it does not need to be checked separately.
  • Since Read Out Loud follows the order of the tags, it can be used to check the tags reading order but not the reading order of reflow view. Note that for most users, the tags reading order can be checked much more quickly using the visual highlighting method described under the previous heading relating to Tags mode.
  • If there are no tags, by default Read Out Loud will infer the reading order from the document and this will generally match the reflow view reading order
  • Users who have no experience with standalone screen reader programs should understand that Read Out Loud’s limited functionality is a pale reflection of the user experience with fully featured screen readers.