Sometimes it is better to find a free PDF editor [Windows or Linux] to do the needed editing for PDF forms and other "interactive" PDF files.
LibreOffice is a great office package, but it was not meant to do everything. [Unlike MSO wants to become]
To do "everything", LO would become a very large install that would be too packed with options that would make it too "complex" for a lot of users, since the navigation menu[s] would be so large and layered that you could get lost in them trying to find the option you want to use.
For me, I use dedicated packages for things like web page development and modification. Writer can do this, but having a package that only does HTML and web page scripting seems easier to use. I also use dedicated packages for image/photo editing and another one for "raster" based image editing. I never learned to use Draw for my needs, since I have been using other product[s] for more years than LO has been out.
I use LO a lot, but like a large percent of its users, I used it for word processing [Writer], spreadsheets [Calc], presentations [Impress]. When I go beyond the "basics" of each module, I tend to fall back to both paid and free packages that I have been using for over ten years, through the original packages and their upgrades.
We all choose the software that is best for our needs, one reason I choose LO. But unless you created a PDF form with Writer, I would use a package that was meant to edited PDF interactive forms. There are free ones out there. It is worth a look-see.