I have the full Creative Cloud subscription, which I upgraded to specifically so i could edit PDFs without having to use Photoshop (which is a very unwieldy process). I have Acrobat Pro DC. I am unable to find any other versions of Acrobat available for download, and the version I have installed will not allow me to add text to the document. How do I find the version of Acrobat that I need? (the error message says something about LiveCycle Designer which does not appear to be in my Apps list...)
This has nothing to do with Acrobat. Protected documents simply cannot be edited this way and PDF isn't meant to be an editable format in the first place, so options are always limited to begin with.
LiveCycle Designer is a unique app that makes special forms which are embedded in PDF. There is no alternative to it.