PDF stands for Portable Document Format and was designed to be a universal document format that could be read by any computer or operating system, whether it is an Apple or Windows based computer. Many people like the way that PDFs provide information that cannot be (easily) changed or edited. However, this can also make them inaccessible to some individuals using assistive technology. This is especially true when a PDF is made of a scanned document.
Saving a document from Word or other format directly to PDF will be only as accessible as your original document.
When sharing or posting a PDF document, a Word version or other version should be posted along with it or information provided as to how someone would obtain it.