The best way to create documents for the web is to create your documents in Microsoft Word.
The reason for this is Microsoft Office has a built in Accessibility Checker that you can use to help ensure content is accessible.
After a documents accessibility has been verified in Microsoft Word when the document is saved as a pdf file the accessibility features will carry over into that format.
Adobe Acrobat has tools to add accessibility to documents as well. However, these tools aren’t as easy to use or as straightforward as the accessibility tools inside of Microsoft Word.
If you try to make a pre-existing pdf document accessible, it often doesn’t work well and it can be a very confusing and frustrating experience.
Since most pdf documents generally originate from a Microsoft Office program, try to add accessibility inside of the original document rather than trying to add it in after the fact using Adobe Acrobat.
Only try to retrofit an existing pdf document with accessibility features as a last resort if you don’t have access to the source files. In most cases it will be much easier and less time consuming to add in accessibility using Microsoft Word.
Although Google Docs is a great program with many useful features, it doesn’t have the tools to ensure accessibility the way Microsoft Office does. Therefore, it is recommended to only create content in Google Docs as a secondary option when Microsoft Office isn't available.