Compacting pdf files

I often need to upload or send files via eMail and often run into file size limits for reception, as well as time-outs for transmission. I'm seeking recommendations for file compression on an Ubuntu 9.4 platform, running Open Office 2.4. For now I need to focus on .pdf, .doc, .peg and presentation files e.g. .ppt, but .jpeg, .gif are also important.

Thanks.

If you select the files you want in your file browser, right click, and go to "Create Archive," you can create a compressed archive that way. The default option is gzip copression, but you can choose others. You can also use gzip from the command line.

a) Mike suggestion is a right one, more in deep in this I can add that there are more than one compression application, and also plugins like 7zip, to add higher compression rates; surely the adressee must have application dealing the same extension, but many, not all are available also on Mac and win;

b) another one is managing to do a more spare use of resources avoiding excesses in dotxinch before saving the file:
1- for web publishing a 72-75 dpi will suffice;
2- for a draft/normal print a 150 dpi;
3- for very high quality 300-600 dpi (art print);

-for only high quality .tiff there is no solution, but
that's only for art paintings reproduction.