I live in Poland but I am mostly working contracts outside Poland or for foreign companies.

When I receive negotiated contract for signing it is usual to expect the contract has already been at the very least initialed on every page by the other party. And I always initial every page of the contract whether the other party did it or not.

Signing every page is not required for the contract to be enforceable but is standard practice.

It's common in several European countries including Belgium and France.

And it is idiotic, of course.