Can I stick or staple landing pages in my passport?

I have landing lips from Macau and Hong Kong. When these landing sheets were first introduced, they were stapled into your passport, now you are just receiving a piece of paper.

I would like to save them for future use (such as testing my travel history by requesting some visas), but I am sure I will lose them if they are not in my passport. That's why I want to stick them or staple them in my passport.

Is it allowed or considered as manipulation and should not this be done?