Certification over digitally signing or using a timestamp allows for more granular control over which features of the PDF remain unlocked. To Certify within PDF Extra:
- Open PDF Extra, tap Fill & Sign
- Tap the Certify option
- Choose your certificate from the next page
allows you to access the signature options such as digest algorithm, Signer, Location and Timestamp Server as well as lock the file from further editing.
option keeps record of certificates you've used in the app.