[pdftex] post-pdf operations?

[Karl Berry]

I have two pdf-related questions, about postprocessing pdf files rather
than pdftex itself, but since I only use pdftex in the context (no pun
intended) of TeX, I'm asking here first :).

1) sometimes, I have pdf files that were first generated as standalone
   documents, but now I want to include them in another document.  Is
   there a way to crop the surrounding whitespace (the margins), so that
   the document is trimmed to just the text?
   
   Right now, I can get the same result by explicit kerns maneuvering
   the image around and playing with the image scaling factor, but this
   is painful.
   
   It's possible to do this with images with the pnmcrop utility, but of
   course converting pdf to pnm rasterizes the fonts, so when the result
   is scaled again, it is unusably ugly.
   
   I tried various combinations of pdf2ps/pdftops, followed by
   epstopdf/ps2pdf, among other things, with no luck.
   
   I see that Elisabeth Baker asked this same question in September,
   with no answer:
http://www.tug.org/pipermail/pdftex/2003-September/004418.html


2) In TUGboat, we try to run articles together to save space, so that
   sometimes one article ends and another begins on the same physical page.
   
   In general, it's not possible to process multiple articles in the
   same TeX run, because of conflicts in the packages, fonts, etc.
   (Believe me, we've tried.)
   
   So, the question is, is there a way to overlay two pdf pages into one?
   
   As far as I can tell, texexec --combination will paste up
   several pages onto one, but we need to layer them over the
   other.  I couldn't find anything else related.  From Planet PDF
   (http://www.planetpdf.com/mainpage.asp?webpageid=453), it seems this
   sort of thing should be possible, but I can't translate those columns
   into commands to run.

I'm most interested in free software solutions, but if there are
commercial solutions, I'd like to know that too.

Any help appreciated,
karl