PDF Creator | https://www.pdfforge.org
This is a free offline tool to write PDFs/JPEG/PNG etc. This application has to be downloaded from their website and installed in the system. The PDFs can be generated with locked feature. This is one of the best PDF writer to create PDFs / JPEG / PNG etc.
There comes one another application with this "PDF Architect" which is very useful for conversion of documents to PDF very easily. However, conversion from PDF to other applications require a license.