Signature authorization is needed for signing specific documents and Power’s of attorney. With your signature authorization you confirm your identity.
For arranging signature authorization you don’t need to visit notary offices. The Czech post office has notary services called CZECH POINT. Authorization of the signature of one document cost 33 kč. You can arrange it at any post office and you should bring your passport and residency permit. The Czech post office has an appointment system and it is in English.
Here you can book your appointment for Czech Point service before you go to the post office: https://www.postaonline.cz/en/rezervace
After they call your number you should say at the window – Potřebuji úředně ověřit podpis.