Document format issues: characters are overlapping in the header ofsome tables

Hello, 

I'm reading this document PostgreSQL 12.2 Documentation(postgresql-12-A4.pdf) which I've downloaded from the official
websitewww.postgresql.org. 


I found some format issues with the table headers in these pages,
1159,1160,1161,1162,1163,1164.

In the table headers, some characters are overlapping and it's difficult to recognize the words. 

Regards,
Ruihai