When uploading attachments into a form submission, only PDFs are accepted at this time.

Attachment fields in Dashpivot forms will not accept the following file formats:

In addition to this, if your PDF file is:

You'll need to remove the password/encryption before you'll be able to successfully upload it into your form submission. Attachments cannot be encrypted because they wouldn't be able to be included in form exports.

If your PDF is password protected, you will get an error message 'Attachment cannot be processed'

Tools like Adobe allow you to remove the password from your PDF files, in addition to a number of free tools on the internet.

Here is a help guide for removing passwords from PDFs in Adobe: https://www.adobe.com/acrobat/resources/how-to-remove-pdf-password.html

Once your password is removed, you will be able to successfully upload your attachment within the form submission with the new file.