How do door seals work?
How do they prevent pressurized air to leak from the doors?


They don't. The seal does not have to be perfectly airtight.

The requirement is that it will create enough impediment to the air that wants to gush out, where "enough" is defined by the capability of the conditioning system to input new air into the cabin.

In other words, everything is fine as long as the air mass that gets out of the doors is less than the maximum air flow that the air conditioning system can input into the cabin.

Note also that, as stated on Wikipedia, aircraft are equipped with one (or more) "out-flow valve(s)" and "pressure relief valves": these valves intentionally let air out of the cabin to avoid over pressure in the cabin and thus they prevent possibly dangerous scenarios.