How to encrypt pdf files with CA?

how do I encrypt pdf files with CA?

requirement: CA manufacturers must obtain administrative license for electronic certification service of the Ministry of Industry and Information Technology

I searched around, but I didn"t have a clue. Let"s ask the boss.

Thank you.

Mar.25,2022
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e44a79-4425b.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e44a79-4425b.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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