You can usually save a copy of a PDF. If the creator of the document assigned additional usage rights, you can save comments, entries in form fields, or digital signatures that you have added to a document. If usage rights have been expanded or restricted, the document message bar under the toolbar area describes the assigned privileges or restrictions when you open the document.
If the file permissions allow, you can also save the contents of a PDF in text format. This allows you to reuse the text from a PDF document and to use the content with a screen reader, screen magnifier, or other assistive technology. For more information, go to these topics on the Adobe website: Save comments, form field entries, and digital signatures and Prevent losing changes to a PDF.