The best practice is to start with an accessible file, such as a Microsoft Word document or PowerPoint presentation, before converting it to Portable Document Format (PDF). If you do not have the original file, contact Instructional Design & Technology for assistance.
The same elements that make Word files, web pages, and so forth accessible apply to PDFs as well. These include organizational structure, links that are embedded, alternative text for images, clearly structured tables, etc.
Tags add an invisible layer to a PDF that is important for conveying its hierarchical structure. Similar in purpose to headings for a web page, tags allow assistive technology such as a screen reader to identify the type of content (text, images, etc.) in the document as well as the correct reading order.
Searchable text is also important for ensuring that a PDF is digitally accessible. Screen-reader technology must be able to read the text aloud to someone who is blind or visually impaired. If you scan a few pages of a book, the resulting file may contain images of text rather than actual words on a page. However, optical character recognition (OCR) software can convert the images to text.
Starting from Scratch
If you are creating a PDF from a file originally authored in a program such as Microsoft Word, PowerPoint, or Excel, refer to the navigation menu in this guide for information about organizational structure, links, and images. When you then save the file as a PDF, generally speaking, the accessible elements will be intact.
If you do not have the original file or are adapting a file with scanned images (for example, a few pages of a book), use a program such as Adobe Acrobat Pro or OnlineCR.net to make the file editable, then proceed. When in doubt, feel free to contact Instructional Design & Technology for assistance!