Error 109 after adobe scan

I have a problem where my digital signature (supplied by a 3rd party) will trigger a 109 error to the signed pdf, but only if I scan the document with adobe scan for ios. I scanned the same document with adobe scan for android, signed it, it worked faultless. I have the same problem with adobe scan on iphone and ipad ... I need my ios app working because all my work documents are on my icloud. PLEASE HELP