This feature is not exactly in Telerik Reporting scope
and our recommendation would be to use a third party tool for combining the pdf pages into one document.
On the side note, you can
modify the report rendered in PDF prior serving it to the viewer - Modify exported report document prior serving it to the viewer client
Telerik by Progress
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal
and vote to affect the priority of the items