You can now attach files to library workouts and plans, planned workouts and other calendar events and activities. These might be instructions on how to do some gym work, test results or anything else. Look for the paperclip icon.
Attachments on workouts in your library or on a training plan are copied onto planned workouts on athlete calendars.
Add attachments to activities on the activity data page:
You can also add attachments to notes and other calendar entries.
I finally found this on attaching PDFs with, e.g., test results, to activities – but they are fairly hidden… 
At the same time we have the paperclip “attach image” on the activities’ overview page… could you please enable that to attach a PDF and show a hyperlinked preview, or even just the hyperlinked name, of the the PDF in the comments area.
That way the attached files would be much more obvious and accessible.
I have been doing that a bit myself by simply manually putting the hyperlink to the file into the comments, but that does not serve as an actual hyperlink as it is text-only and I also fear that these specific URLs might change sometime. Also, the whole “googleapi” URL is not necessary for display, just the filename leading to the file itself would be a better, easier to grasp, description of the content:-)
I have added support for file attachments in chat (all chats, not just on activities). I will deploy Monday AM (GMT+2).
