PDF document security and digital signing via C #

Question

Hello,

I created a PDF in c # using namespace PdfSharp pulled off the web.
Now I want to secure the document and set a 'Not Allowed' for a number of security parameters (such as 'Content Copying',' Page Extraction' and more),
and add a digitally sign the document.

All this through code in c #.

Can anyone help?

Thank you!