This is the 10246th most frequent Turkish word.
belgesine
"Belgesine" means "to its/her/his document" or "to the document" in English.
The word 'belgesine' here means 'to its document' where 'belge' means document. It's used with a possessive suffix referring to something that belongs to the booklet and a dative case suffix indicating direction.
Bu kitapçığın sonunda bir ek belgesine ulaşacaksınız.
At the end of this booklet, you will find an additional document.
In this sentence, 'belgesine' refers to 'to a documentary belonging to...' which is shaped by the possessive and dative case modifications, contextualized around a topic.
Vadinin doğal güzelliklerine dair bir belgesine katıldım.
I participated in a documentary about the natural beauties of the valley.
'Belgesine' in this sentence indicates 'to or into a document associated with...', utilizing the same grammatical possessive and dative cases but conveying ownership or connection.