How can I add a restriction site to a primer while ensuring it does not interfere with the primer's function?

To add a restriction site to a primer without interfering with its function, you can place the site at the 5' or 3' end of the primer, away from the region that binds to the target DNA. This way, the restriction site will not disrupt the primer's ability to anneal to the target sequence during PCR or other molecular Biology techniques.