Introduction
Apitron PDF Kit is an outstanding library for all kinds of tasks related to PDF, it offers well-designed and balanced API that follows the specification as much as possible at the same time making your life easier by automating many routine operations.
We decided to take it one step further and introduced Apitron PDF Kit open source extensions library which would automate most frequent pdf manipulation activities, and started with adding digital signatures and watermarks.
The project pursues two main goals:
1. Make PDF processing more intuitive and straightforward
2. Show how the base Apitron PDF Kit API works using real-life examples
The source code for the library can be found in our github repo by the following link. We will probably wrap it as a nuget package later, but for now you can just checkout the code and compile it yourself.
Code samples
Signing is very simple and consist of a one line call of the method Sign, you provide the certicate, password, signature image and its boundaries and a few optional params if needed.
using (Stream inputStream = File.Open("../../data/letter_unsigned.pdf", FileMode.Open))
{
using (FixedDocument doc = new FixedDocument(inputStream))
{
doc.Sign("../../data/johndoe.pfx", "password",
"../../data/signatureImage.png",
new Boundary(100, 140, 190, 180), outputFileName);
}
}
And the result:
 |
Pic. 1 Signed PDF Document |
Same applies to stamping a document with a transparent watermark, just add a one-linecalland voilà:
{
using (FixedDocument doc = new FixedDocument(inputStream))
{
doc.Watermark("../../data/watermarkTransparent.png", outputFileName);
}
}
The result is below:
 |
Pic. 2 Stamped PDF document |
Summary
If you need to incorporate the basic PDF processing functionality into your applications, then the open-source Apitron PDF Kit extensions library we’ve published a few weeks ago could be the right choice. It saves time keeping things simple, and you can always fallback to the main API if you need something going beyond its capabilities.