How to implement 'timed' PDFs and other custom document permissions using PDFNet SDK?

We are a publishing house and we would like to sell technical papers
on the web.

We would like to have timed versions of PDF files. Also we may want to
add additional custom permissions related to printing (e.g. the # of
times the document can be printed, etc). Can this be implemented using

Using PDFNet SDK you can could restrict PDF documents so that they can
be viewed only within certain time period or with arbitrary custom
permissions. In this case you would need to implement a custom PDF
viewer using PDFNet (e.g. as illustrated in PDFView sample project:

To prevent user from opening the document in Acrobat and other PDF
viewers, you would need to implement a custom security handler by
implementing a new SDF.SecurityHandler or by modifying standard PDF
security mechanism (SDF.StdSecurityHandler).