that you want to upload documents to the site so they can be downloaded by your site visitors there's no problem. You can use one of the many available FTP programs to create a new directory on the server, and transfer the documents into it. If you have a lot of documents it's helpful to create two directories - one for Word docs and one for PDF's. Then you'll need to create html hyperlinks to each document. Clicking on one of the links will make a visitor's browser open a download dialogue box, and the document is transferred to his/her computer. Provided the person concerned has the same version of Word as the one in which you created the documents (or a later version) there'll be no problem - all formatting will be preserved.
PDF documents will be readable by anyone, as long as they have Adobe's free PDF reader installed. It's usual to put a hyperlink to the Adobe reader download location near your PDF hyperlinks, so users can get the reader if they don't already have it.