Something to try -- With Acrobat XI use the Edit Text and Images tool.
Use a copy of PDF files you have available.
When the tool is in use you will observe "boxed" content.
You can touchup within the "boxes".
Play with it.
I suspect you'll come to tell Toto that y'all aren't in word processor format any longer.
While Acrobat provides robust support for touchup of characters and character strings word processing like "editing" isn't an option. PDF (defined and described initially by Adobe's PDF References and now the ISO Standard ISO 32000) is not a word processor, spreadsheet, or page layout file format. Consequently PDF does not tolerate word processor like "editing". Attempting to do such can goober a PDF into something unusable.
To convince yourself use work copies of PDFs you have. Play "editor" with the Edit Text and Images tool. Where you drop off the blue event horizon is tends to be a function of the relative simplicity or complexity of the mastered content from back in the authoring file. Kinda gives new meaning to "measure twice, cut once" in context of the work done in the authoring files.
Be well...