@RezaRaoofi answer was exactly correct when he wrote it two hours ago, but I just updated the docs and moved the information regarding PDF attachment archiving to a new article. See help.appsheet.com - Email PDF Attachment Archiving
One word of caution. When we were archiving the PDF attachment, we were not properly honoring the value specified in the “Default app folder” property on the Info > Property pane.
We attempted to do so, but ended up storing the PDF attachment in the wrong folder.
I have just made a change to correct this problem last weekend.
When I make such a change, I release it to a few customers at a time.
If you wish to be included, please provide your account id and I will include you in the “Rollout”.
Email PDF Attachment Archiving help.appsheet.com