When placing electronic signatures, it is important that the PDF does not contain errors or active elements. Viewing a PDF is a different process than sealing and signing it.
A few things to keep in mind:
The PDF should be flat, so no annotations, attachments or elements such as layers;
The PDF should be without syntax errors. This can be checked in PDF tools such as Adobe Pro, with Preflight;
If electronic signatures are already present before uploading, it is important that they are compliant with PDF standards;
The PDF should not be restricted with a password or other protection;
Very old versions of PDF might give problems, because they support less modern syntaxes. The current version of PDF is 1.7;
We support PDF/A.
Most of these scenarios can easily be tested by uploading the file and sending yourself a sign request in our portal. If signing completes and a signed PDF can be downloaded, you can assume your PDF's are correct.
Resaving a PDF, or printing to PDF, can solve some problems as well.
Please contact our support team if the steps above do not result in successful signing via chat or e-mail: support@signhost.com