A web-based open source software to compress PDF files, to submit files via a browser, but to install on my own Linux server and use its processing power.
A web interface. A command line software is acceptable as a last option because I can develop the web frontend, but I don't want to reinvent the wheel.
Linux compatible, regardless of the programming language.
Be able install it on my own server.
What I already know and found
Ghostscript: Linux compatible, I can install on my own server and it's open source. Obviously, since it is only a command line software, web interface is a feature that I will have to develop apart. (my best option, so far)
3-Heights PDF Optimizer: Linux compatible, I can install on my own server, doesn't include a web interface but offers an API. Same cons from Ghostscript and it is not open source. (used in smallpdf.com)