In the past, I've used Adobe Reader which I think allowed me fill in text fields for a PDF document.
This blog entry has some download links on Adobe site to the older PowerPC version:
http://yappcblog.blogspot.ca/2016/06/acrobat-reader.html?m=1
Be careful because Adobe may install some other software that you might not necessarily want on your computer.
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To me, editing a PDF document and filling in text fields are two different things...
Filling in text fields
Why we would need "text fields" in PDF documents is certainly questionable, but I know I had to fill out a PDF text form also and was in the same quandary. Sometimes, it was much easier to print the PDF (on paper), and fill out the fields on the printed document with a pen, and scan the paper document back in — and save it as a PDF!
Editing a PDF document
"Editing" a PDF document isn't just about simply filling out text fields. Editing the actual PDF is a different animal altogether. I needed to change some of the text in a PDF and have it still aligned and formatted the same as the old text. I "edited" the PDF document with a program on Linux (I forget which one), but it was fraught with problems, but I did eventually manage to "edit" the PDF.