Webstandards, Accessibility and Usability at Penn State

HTML versus PDF

PDF Files are a convenient way to deliver print documents online, but should generally not be used a replacement for an HTML Web environment.

Potential Disadvantages include

1. PDF documents are usually formatted to printed vertically, but computer monitors are generally horizontal. The mismatch causes users to scroll more often than in an HTML site which can be difficult for users with mobility impairments.
2. Very large files can be slower to download than an HTML page.
3. PDFs consiting of scanned pages is really a series of images, and inaccessible to a screen reader. Only an OCR (optical character reader) scanner can can save a scanned document as a text file.
4. The interface between a browser and an PDF file is not consistent across platforms and browsers.
5. The transition between a PDF document and an external Web site is not as seamless as between HTML documents.
6. PDF files may need to be tagged in order to be considered accessible to screen readers.
7. Additional training and plug-ins for making PDF forms accessible is required in addition to the training needed to make an HTML form accessible.
8. PDF interfaces can be slower to zoom than an HTML version, particularly for complex documents such as a street map.

However, there are instances when a PDF file is the best way to deliver material.

Some good uses of a PDF File

1. Post print manuals and print forms online. These would include blank tax forms, how-to instructions for designed print, blank application forms, contracts, long articles or long users manuals.
2. Post material using technical fonts in specialized fields such as in music, foreign languages, mathematics, and so forth.
3. Deliver high resolution images in a relatively small file format.

Synopsis

In order to make the use of PDF files more accessible, consider these recommendations.

1. Always provide a link to the page to download Adobe Acrobat Reader.

   SECTION 508 - When a web page requires that an applet, plug-in or other application be present on the client system to interpret page content, the page must provide a link to a plug-in or applet that complies with § 1194.21(a) through (l).

2. Convert files to be compatible the latest versions of Acrobat Reader since more accessibility options are available. Encourage users to download the latest versions of Acrobat Reader.

3. Note when a link goes to a PDF file (e.g. "User's Manual (PDF)"). This gives notice to all users that a link will be opening a PDF file, not going to another Web page.

4. Create files compliant with more recent versions of Acrobat Reader and use "tagging" to make sure all images have the equivalent of ALT tags. These tags can be accessed by some screen readers. Instructions are available from Adobe Acrobat Accessibility. See the Section 508 paragraph from the previous item.

5. Create a PDF file directly from a Word or text file whenever possible to enhance accessibility because the content will be stored as text and is more likely to be accessible by a screen reader.

6. If you use Microsoft Word, use the Header 1, Header 2, Header 3 styles where HTML would use H1, H2, H3. When these documents are converted to PDF, these styles will be parsed as headers.

7. Recent versions of Adobe InDesign (Mac and Windows) supports tagging when PDF files are created (or exported). Recent versions of Micorsoft Office for Windows also includes some additional PDF tagging features.

8. If you are scanning in material which is mostly text, scan the material in with an O.C.R. optical character scanner which converts a scanned image of a text to a text file. If files are scanned with a regular scanner, the PDF file will consist of a series of inaccessible images.

   Note: Scanning text with an OCR scanner will also make the transition of any text to HTML easier.

9. Avoid converting text with multiple columns into PDF This causes addition scrolling up and down as you read each column making it harder to process for people with motion impairments.

10. Be aware that some security measures on PDF files may disable screen reader access. Be prepared to provide alternative access to visually impaired users.

11. When in doubt, provide an alternative text-only or HTML only format which is more likely to be accessible.

12. Read more about how to optimize PDF files for accessibility. Some resources include the following:

P.D.F. File Accessibility Links

• Adobe Accessibility
• Adobe How to Create Accessible Adobe PDF Files
• University of Wisconsn Making PDF Files Accessible
• A List Apart Facts and Opinions About PDF Accessibility
• Making Connections - U.K.
• Planet P.D.F. Accessible P.D.F.

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