Questions & Answers about Tutaj trzeba złożyć podpis.
Trzeba is an impersonal word meaning it is necessary, one must, or in natural English often you need to.
In Tutaj trzeba złożyć podpis, there is no specific subject like I, you, or we. Polish often uses this kind of impersonal structure when the instruction is general:
- Tutaj trzeba złożyć podpis. = You need to sign here.
- literally: Here, it is necessary to place a signature.
So the sentence does not name the person explicitly, but in context it usually means the person filling in the form / reading the instruction.
This is about aspect, which is very important in Polish verbs.
- złożyć = perfective
- składać = imperfective
With trzeba, both aspects are possible, but they give slightly different feelings:
- trzeba złożyć podpis = you need to complete the act of signing
- trzeba składać podpis = would suggest a repeated, ongoing, or habitual action, which does not fit this context well
Since signing is a single completed action, Polish normally uses the perfective złożyć here.