What does PDF metadata mean for your PDF?
Open any PDF’s properties and you will usually find a name — often a computer account name nobody chose to publish — plus the program that produced the file and two timestamps.
Metadata travels with the file through email, cloud storage and print services. It is the most common way an "anonymous" document stops being anonymous.
Clearing it changes nothing about the pages. You can also set the fields deliberately, which is what archives and document management systems expect.
How do you see what a PDF is carrying?
Every reader shows it, usually under File → Properties (Ctrl+D in Acrobat, Cmd+D in Preview). The panel lists title, author, subject, keywords, the application that made the file, and the created and modified dates.
The author field is the one that catches people out. It is filled in automatically from the account name on the computer that made the file, which on a work laptop is often a full legal name or an employee ID nobody chose to publish.
Worth knowing: the panel shows one of the two places metadata lives. A file can also carry an XMP packet with a second, different set of fields, and some readers show that one instead.