In that case, the Xway part of this question is that you would add an external link to a PDF that you and other group members would upload separately.
Some kind of content management is then needed to allow group members to edit and/or reupload the PDF file. A simple way to do this might be to create a separate folder that group members have access to via an FTP client - as @waltd previously suggested. This folder would contain the PDF file. If you named it “marketplace” and put it in the same directory as your index file, you could link to it from Xway using an external link such as https://[domain-name].com/marketplace/[file-name].pdf