PDF Digital Signature Validation

Did you ever receive a PDF document which is digitally signed? When you open this document in Adobe Acrobat Reader, you'll notice that it is validating the document by showing a very small 'green checkbox' in the top left corner. Something like this:

Signature is valid

Ok, great, but what does it mean?

It means that this document has been 'digitally signed' or better, somebody has used 'a digital certificate' to perform 'a signature' on the content of a PDF document.

Hold up, what do we mean with a 'digital certificate' and where can I find them?

Simply put, a certificate can be seen as an electronic document which you can use to authenticate or digitally sign. A digital certificate contains information about an identity. You can find these certificates on EU national ID cards for example, or you can buy them from a Certificate Authority (CA), if you require legally binding signatures.

Now, how does that work? And how can I validate digitally signed PDF documents using an API?

This tutorial will explain:

• how to validate documents in Adobe Acrobat Reader.

• how to perform the same validation of digitally signed document in your own application.

For the latter, a step-by-step approach will be used. An example of an implementation is provided on Github:

https://github.com/Trust1Team/vwapp

The application is available online.