I thought PDFs weren't made to be edited? why not just copy and paste in a word processor and save as a PDF?
Technically they aren't. You use a native app and then save or export a PDF. In this case Word, but other apps (as was mentioned) can be used.
To edit a PDF you need either Acrobat Standard or Pro on a Mac or PC. Even then, depending on the complexity of the PDF the standard editing tools don't always do the job. That's where plugins like Enfocus Pitstop Pro come in. If you've got about $800-900 to drop on a plugin.
I don't think there's anything equivalent on iOS to make the kind of edits you can on a computer using Acro Standard or Pro.
Reader definitely doesn't cut it for anything except reading.