Thank your for the interest in RadPdfProcessing.
Currently it is not supported to create PDF documents from TIFF images. I added your request to our backlog and we will take it into consideration. In addition you can track the progress on this using this item in the Feedback & Ideas portal.
Hope this answers your question.
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time. Watch the videos
and start improving your app based on facts, not hunches.