I know that probably no information is passed to the PDF when a .tex file is compiled, but is there a tool that can convert a PDF document to (La)TeX?
If you install AbiWord with the additional import and export plugins,* you can open a PDF file in the Word Processor, and then export to LaTeX. In fact, you can also convert from the commandline:
Be warned that both its PDF import routine and its LaTeX export routine have serious limitations, and you should not expect anything that will useable without serious tweaking afterwards.
(* IIRC, the extra plugins are installed by selecting a custom install on Windows and checking all the import and explort options it gives you. For Linux, you typically need to install a separate package called "abiword-plugins" or "abiword-plugin-mathview" depending on distro. No clue for Mac.)
Inkscape can open PDFs and export to either PSTricks or TikZ codes; this might be useful if the PDF in question is just a diagram or vector image you want to edit.
There's a project listed on sourceforge called pdf2latex, but it doesn't look like any real work has been done on it. I'm not sure it's a real project. (The page looks fishy; almost as if someone was just posting an idea.)
Check out InftyReader.
Quoting the start page:
Import the file using LibreOffice. It will create a Draw file. You have to copy and edit it by pieces into Writer. Then you can use the plugin
If your docs are large enough, this process might be easier than re-typing everything.
Another alternative, if you are dealing mostly with pure and simple text, is to save the file as a