Learn Italian: C'è qualche link utile in questo documento? - Is there any useful link in this document?

The word qualche (meaning 'some' or 'any') is always followed by a singular noun in Italian, even when we translate it as a plural in English. Because the noun (link) is singular here, we must use the singular c'è (is there) instead of the plural ci sono (are there).

Does the English loanword link change if we use it in the plural?

No, foreign words adopted into Italian generally do not change their spelling in the plural. You would say un link (one link) and due link (two links). In this sentence, it is grammatically singular because of the word qualche.

Why does utile end in '-e' instead of '-o' if link is a masculine word?

Adjectives that end in '-e' in their dictionary form, like utile (useful), do not change to match masculine or feminine nouns. They only change to show singular (-e) or plural (-i). Since link is singular here, utile keeps its '-e' ending.

Why do we say in questo documento instead of using a combined word like nel?