I’m sure Robert is aware but for anyone else reading that: you don’t need a Paperpile account to take part in a shared folder. Using the private sharing link everyone can view a shared folder and read the papers in there.
Clearly, at some point we have to draw the line and we can’t re-implement all functions for the use case of somebody not having a Paperpile account.
The “File request” feature is useful for a service like Dropbox. Dropbox is about file sharing and this features solves the problem of sharing large files.
I don’t really think it’s necessary for Paperpile though. You can just ask your colleagues to send the Paperpile by email, Dropbox or Google Drive and you drag the PDF on Paperpile and in the shared folder. That seems not more complicated than any UI that would be necessary for a “file request” feature.
We have plans to implement the email to Paperpile feature eventually, so that workflow should become even easier.