Preview - copy and paste

It depends on the PDF. Some are just images made from scans and don't have any text per se.

Some might be copy protected and don't allow it, either.

I have found that file->copy sometimes works better than cmd-c

I just need to clarify, it sounds like you want to copy PDF text into into a MS Word document and then edit that text. Is that correct? If so there are many products on the Mac App Store that will do that. Just do a search for PDF editor and select one.

Your welcome.