How to add a bit of text to a PDF file?
 

I would like to add a bit of text in the margin of a PDF file, for example a date or web address.

Any tips which tool to use or an example would be greatly appreciated.

Have you tried using Libreoffice ?

or
from the terminal
pdf2ps then edit and run ps2pdf

Sorry, I forgot to add that I would like to do this via the commandline, and, if necessary, convert to PS. I was envisaging storing the text and position in a meta file.

Hi

You could use pdftk and add a pdf "watermark" or "stamp". Make a PDF with the text in the margin, then use pdftk to put the text pdf as watermark (below) or stamp (above).

If you are planning to start with a given PDF file and do a batch run to generate multiple copies of that PDF, each with specific text in certain places (for example, filling out a standard form multiple times), then flpsed may be what you need. It is primarily an interactive editor but it lets you insert named tags at arbitrary places and then do non-interactive batch runs to insert text at those places. The program works with Postscript files, but you can use pdf2ps and ps2pdf