If you post PDFs online, they must be made accessible before being posted so they work effectively with screen readers such as VoiceOver or Windows Narrator. A document or application is considered accessible if meets certain technical criteria and can be used by people with disabilities such as mobility impaired, blind, low vision, deaf, hard of hearing, or who have cognitive impairments. USD policy on digital accessibility
There are many things that can be done in native document applications to support accessibility, such as adding alternative text for images; defining structural headings, lists, and data tables; providing document language; and setting document properties such as titles. Desktop publishing applications such as Adobe InDesign support these features, as well as other word processing applications such as Microsoft Word. Google Docs is not recommended as an authoring tool for exporting as a PDF.
Review the Guidelines for Accessible Documents. The easiest way to create an accessible document is to start with the authoring software it was originally created with such as Microsoft Word, Powerpoint, or Google Doc.