I want to replicate the core functionality of an e-signature software such as DocuSign, HelloSign or SignRequest.
Everything is clear to me, but I have a hard time understanding how does the software works itself. How does it render the boxes over the PDF, how does it place the signature over the PDF when I am done writing, how does that JS signature create a PDF on the server side?
How does these types of software work?
There is an abundance of technologies & tools available to develop such e-signature software. Let's take one example which is somewhat similar to the software you mentioned. The use-case to build such software can be realised using the front-end and back-end (server-side) technologies.
On the Client-side, you can use front end frameworks like Angular and React to develop an interface for the end-users using which they can upload the documents to the server-side. You can create signature block layouts and display them alongside the document. Users can drop those blocks on specific locations and send the request for signing to the recipients. During the signing process, user details will be populated into the signature block and sent to the server for performing the signing process.
On the server side, the responsibility would be to take the appropriate information from the request and print/add those signature blocks to the document at the appropriate positions. On the server side, you need some library to process the documents for adding the signature blocks and signing the documents. If you're using java alongside the spring framework you can use pdfbox for doing such operations.
On server side the responisbility would be to take the appropriate information from the request and print/add those signature blocks to the document at the appropriate positions. On server side you needs some library to process the documents for adding the signature blocks and signing the documents. If you're using java alongside spring framework you can use pdfbox for doing such operations.
How does it render the boxes over the PDF, how does it place the signature over the PDF when I am done writing, how does that JS signature create a PDF on the server side?
The contract between client and server for the signature blocks could be a JSON object having the information about the coordinates where the request creator drops those blocks for recipients for signing. On the server side, you can manipulate the document to add those signature blocks at the mentioned coordinates in the request.
