I have some landings lips from Macau and Hong Kong. When these landing slips were first introduced, they were stapled into your passport, now you are just getting a piece of paper.
I would like to keep them for future uses (like proving my travel history on applying for some visas) but I know for sure that I will lose them if they won't be in my passport. That's why I want to glue or staple them to my passport.
Is it allowed or is it considered as tampering and I shouldn't do this?