Learn Spanish (Latin America): El documento puede revelar su identidad, ¡no lo compartas! - The document can reveal his identity, do not share it!

In negative commands (telling someone not to do something), object pronouns like lo must go between the word no and the verb. If this were a positive command (Share it!), the pronoun would attach to the end of the verb: ¡compártelo!.

Why is the verb spelled compartas and not compartes?

For negative tú (informal you) commands, the verb endings swap. Because compartir is an -ir verb, its negative command takes an -as ending instead of its usual present tense -es ending. So, tú compartes (you share) becomes ¡no compartas! (do not share!).

What does lo mean in no lo compartas?

It refers to el documento (the document). Since documento is a masculine singular noun, we use the direct object pronoun lo to mean it in this context.

The English translation says his identity, but could su identidad also mean her identity or your identity?

Yes! The possessive word su can mean his, her, its, their, or your (formal). Without more background information, su identidad could mean any of these. The translation simply chose his as one realistic option.