This page explains he process of signing a document and what needs to be done.
You should start by walking through our demonstration site as per this link: Demo Site Wiki. As this shows you the process from a user of a signed document. Understanding the basis of this will help understand how to sign documents.
The process of signing requires you to have access to the Private Key for your https certificate. As that is used to sign the documents. If this is an issue (e.g. your site is hosted by a provider who manages that) it is not an issue as we can supply a "signing server" that is hosted on a special domain e.g. https://signing.yourwebsite.com and use that to sign the documents.
If you have access to you SSL private key then the process is reasonably simple. First you compute the sha256 hash of the file you want to sign. Then you use openssl software to sign that hash with you private key. And then send the hash and the signature to our API
For a full demonstration of this see our Direct Signing Demo Wiki
If you do not have access to the SSL Private Key this is not an issue. We have a signing server. You can either request that we host this for you - would be on a domain like https://signing.yourwebsite.com. Since this would be a standalone sub-domain on its own host it would have access to required key. You would then securely send hashes of files to this server which would compute the signatures and send on to umpint.com
We have a full demonstration that is running for our demo site dummybank.co.uk. Details of the demo are here: Signing Server Demo
The source code for the signing server is available here: Signing Server Source Code.