How to trust a signed PDF
If you open a PDF that has been digitally signed, Infix Pro PDF Editor will display various signals. These will help you in deciding to trust the integrity of the PDF's contents.
Green Signal
This is shown in the status bar at the bottom of your PDF (View->Status Bar)
This indicates the PDF has been signed, the certificate used has been verified and the PDF has not been edited since it was signed.
Red Signal
When you see this signal you may want to proceed with caution - the PDF contents may not be the same as they were when it was originally signed. Or, it may have been signed with an invalid certificate.
This indicates the PDF has been edited since it was signed or that one of the signing certificates used is no longer valid.
Signature Details
To see a detailed breakdown of the digital signature applied to a PDF, choose View->Signatures or double-click on the red/green signal in the status bar as shown above.
A PDF may have multiple signatures and each may have it's own certificate. Using the Signatures panel you can view the details and validity of each link in the chain.
Adding New Trusted Certificates
You may be sent a signed PDF which includes a certificate which you have not seen before. If you are confident of it's authenticity (it is from a trusted friend or colleague for example) you may add it to a list of trusted certificates. This means, next time you receive a PDF signed in a similar way, Infix Pro PDF Editor will assume that certificate can be trusted.
In the example shown above, the bottom three entries in the signature tree are individual certificates:
If any of these three are currently untrusted, you can click on each and press the Add button. Be sure that the certificates you add really can be trusted before you do this.