Security? Who wants security?
There is a pretty lackadaisical attitude to security in evidence in the comments above.
Several commentards seem to think the issue of metadata in files is a not a security and privacy issue. "Oh, big deal" they sneer.
Of course it is a security issue. And one, as has been pinted out, that applies to the most common filetypes - including those generated by OO and MSO files - and not a PDF-specific thing.
Regarding the point about revealing OS and app vers, I'd be equally concerned about browser headers - for users of Firefox I suggest a look at the ModifyHeaders add-on here:
http://modifyheaders.mozdev.org/no_wrap/help/en/index.html
Quote:
"Apart from EXIF info, that's actually useful ... "
It can be useful, of course. But, equally, it can be very revealing. I tend to strip it if I send photos anywhere. For a start, it's easier to remove EXIF data from an image file than the metadata from a Word Doc or a PDF.
A good starting point is to ask "Does world+dog *need* this or that information?" If the answer is "no", then strip out the information. Simples.