I have a collection of documents in PDF that are used to build a library of technical manuals. I would like to retain the look and feel of these manuals but edit them in FrameMaker. Is this possible? If so how do I do it?
PDF is a destination, not a journey. PDF does not retain the formatting information needed to do what you are looking for, and PDF isn't an intermediate format.
So, you might try using Acrobat to save the PDFs as Word and wrench on them in Word (though I suspect that will be unsatisfactory). And, you can always edit the PDFs in Acrobat (which will also kinda stink).
Otherwise, you might export the PDF as text, import the text into FrameMaker, and apply your FrameMaker styles there. After you have a good set of source files, you can create PDFs and maintain future PDFs using FrameMaker.
Oh, and images can be gotten from the Word export, from PDF export, or from capturing the images in the PDF using screen capture software.
You can import a multi-page PDF into FrameMaker via File > Import > File one page a time, but you will not be able to edit the contents in FrameMaker. However, if you edit the PDF in Acrobat, and if you imported the PDF into FrameMaker by reference (means: link) then FrameMaker will pick up the edits.
That said, this is a very clunky workflow and I would not recommend it to anyone. I am going to second Sean's recommendation of extracting the contents of the PDFs and then using the contents to create new documents in FrameMaker. If you need details on how to do it, please ask us.