How does one encode attachments of text do***ents in Eudora on a Mac so PCs can read them from emails?

The subject says it. 

I am trying to find some sort of formatting or compression of text file 
attachments that most PC's can access. I have Stuffit 9.0, so I can zip 
files or use UU or tar or several other codings, but a significant 
fraction of my targets complain that they cannot open them.

I also can do .odt and .pdf and .rtf and .txt

Thanks for any help ( or any useful URLs ).