Web Presentation Guide 5.1
PDFs
Action
Effectively use and optimize Adobe Portable Document Format
(PDF) files.
Why
The effective use of PDFs benefits the end user, Web administrators, and the network infrastructure.
If you use PDFs effectively on your Web site, the print-friendly features will benefit the end user, Web administrators and network infrastructure.
What/How
The PDF file format is commonly used for electronic document distribution. Adobe software, either stand alone or embedded as a product add-on, is used to create a PDF document and the Adobe Reader is necessary for viewing. The user must download and install the free plug-in on their computer.
Consider the needs of your audience when determining the file format:
- Will they be reading the document on the screen or printing it?
- Will they need to print the entire document or more likely want to access specific sections?
Consider using HTML for Web-based information unless you must keep the publication or document in a print-ready
format.
PDF preserves all formatting, graphics, fonts, and color of the source document. As such, a file converted to PDF may become too large to download via a slow Internet connection.
Consider the following for distributing PDF files via the Web:
- Reduce the file size using options available from Adobe:
- Compress text and line art
- Lower dpi settings for images
- Lower quality setting to minimum
- Remove fonts from "always embed" list
- Remove extra pages
- Remove embedded tags
- Optimize for page-at-a-time viewing
- For more information on optimizing PDF file refer to the How to Section below.
Download Speed and Instructions
- Configure server software to support page-at-a-time functionality. Information is generally available from server software
manufacturer.
- Configure PDF files for page-at-a-time downloading and viewing "Byte serving" or "Fast Web View" for large files.
- Inform the Web user of the document size and possible extended download time.
- Configure the hyperlink to the PDF document to open in a new browser window to make it easy for the user to close the document and return to the originating Web site.
- Provide instructions on the Web page to explain how to download a PDF document. "To download this document, right click the link and select 'Save target as' and select a location on your computer."
- Provide a link to the Adobe Web site to download the Reader plug-in.
- Provide the user with different download options. Offer the document as one large file and a collection of smaller documents.
- Note that when a large document with internal hyperlinks is broken into smaller documents those hyperlinks may not work unless all smaller documents are downloaded.
Compatibility and Accessibility
- Ensure that the PDF is compatible with older versions of Acrobat Reader by reducing the file size. Go to Advanced | PDF Optimizer |Reduce File Size to perform this function
- Add the title, subject, author, and keywords to the PDF document information properties for searchability.
- When hyperlinks are indicated in the documents as active (e.g. blue underlined), activate the hyperlink capability in Adobe Acrobat.
- Use Acrobat's built-in tools to check your PDF document for Accessibility for individuals with disabilties before distributing to the Web. The plug-in utility allows assistive technology such as screen readers to interact with the PDF document. The "make Accessible" plug-in converts untagged PDF to tagged Adobe PDF which can be read by a screen reader. Tagged Adobe PDF can also be reflowed and/or saved into Rich Text Format (RTF).
Performance and Reference
- Use PDF Maker (distributed with Acrobat) for best performance with converted Microsoft documents.
- Use Acrobat Distiller for best performance with converted postscript documents.
- Provide a link to the originating site within the PDF so the viewer can easily return.
There are many features to help reduce the size of PDF files. Which ones you use depends on the intended use of the file, and essential properties it must have to fulfill those functions. In most cases, the default settings are appropriate for maximum efficiency. Compressing images, removing some embedded fonts and unnecessary items from the file provide the greatest opportunities for saving space.
Run a space audit before you begin optimizing to provide a report of the total number of bytes used for specific document elements (fonts, images, bookmarks, forms, named destinations, and comments) and the total file size. Results are reported in actual bytes and as a percentage of the total file size. The space audit results may give you ideas about where you might be able to reduce file size.
To audit the space usage of an Adobe PDF file:
- Choose Advanced > PDF Optimizer.
- Click the Audit Space Usage button at the top of the dialog box.
- Click OK when you are done reviewing the information.
Note: If you optimize a digitally signed document, it invalidates the signature.
To optimize Adobe PDF files:
- Choose Advanced > PDF Optimizer, select a version of Acrobat that the PDF will be compatible with from the Compatible
With menu.
- On the Images tab, select the options you want for color, grayscale, and monochrome images. Or, select Enable Adaptive
Compression at the bottom of the tab and drag the slider to a position representing the balance you want between
Compression and Quality.
- On the Fonts tab, un-embed any fonts that aren't needed, such as fonts that you know are already installed on the
computers of all users who will need them.
- On the Clean Up tab, select a Compression Option and then select check boxes for the items you can remove or discard
from the file.
- When you finish selecting options, click OK.
Note: To restore defaults for all options, click Restore All Defaults at the bottom of the PDF Optimizer dialog box. This restores the defaults on all three tabs as well as the Compatible With option #6. In the Save Optimized As dialog box, click Save to overwrite the original file with the optimized file, or select a new name or location.
The PDF Optimizer options are comparable to the options available when you create an original Adobe PDF file using Acrobat Distiller.
Checklist: PDFs
Resources
Related guide topics