You need the full blown application to edit, you probably only have the reader? You can paste it into another app and have at it there, but formats and such will probably not be good.
PDF files aren’t meant to be edited. Some PDF files are stored in a format where some minimal editing can be done. You may want to try OpenOffice with the PDF import extension.
If you do not have the full package, i.e. :Adobe PRO, google “Bluebeam software” and downlaod their “Trial Version”. Much cheaper than Adobe and many other options.
Then again as other said, the file may be set to not allow much if any editting.
What about the dumb guys reading the question? I would not know how to begin to edit a PDF file. I didn’t know they could be edited. See how much I learned because you asked a “dumb” question?
As stated earlier, most PDF files can’t be edited. Some however are created in a specific way to be edited. Even if they aren’t guys(like me) who have the appropriate software can edit them with some level of ease.
At my job, I create PDF files all day long for our workflow. Every one of them can be opened and edited/adjusted at will.
Adobe’s market plan is simple. Everyone can read their document free of charge, but if you want to right a .PDF document, it costs big-time for a full-blown editor.