What is the Best Free/ once off paid for Pdf Editor program

Depends what you want to produce. For quick-and-dirty single page documents, I use OpenOffice and export as a PDF; for more complex publications, I use ancient Serif software that's still as good as the day I downloaded it (DrawPlus and PagePlus). Based on recent positive experience with their alternative to Photoshop, if I was starting afresh, I'd stick with the same stable, now re-branded Affinity, and pay for their Publisher package. https://affinity.serif.com/en-gb/publisher/

Ah right. I think OpenOffice is likely to do the same, and Affinity Publisher is probably way too powerful. For that kind of thing I do use it's predecessor (PagePlus) but only because I have it for producing PDFs from scratch.

In some cases, it's more how the PDF has been encoded that's the problem with the formatting than Word's limitations. A workaround can be to import the PDF page as a picture and place your filled fields over the top.