This is the 5177th most frequent Turkish word.
imzalı
Signed.
Here, 'imzalı' means 'signed,' describing the document as bearing the signature of someone prominent.
Bu belge ünlü bir yazardan imzalıdır.
This document is signed by a famous writer.
In this case, 'imzalı' modifies 'form' to indicate that this form has been signed by someone specified in the context.
Ona, senin imzalı formunu vermesi için söyledim.
I told him to hand over your signed form.
Here, 'imzalı' denotes 'signed' paintings, indicating that these artworks have signatures, possibly of their artists.