Secured/Protected/Locked PDFs are not Accessible
What are Secured/Protected/Locked PDFs? These are documents that the author restricts from modification or copying text when it is published electronically. If your PDF contains sensitive information, such as personal data, it’s important to ensure that it is protected from unauthorized access. But if your intent is to share information from the document, leaving your document unlocked provides wide access to its content by persons with disabilities.
A locked document prevents a screen reader from working to read the content.
If your document was sourced from someone else, try to request a document that is not locked or search the internet for a version that is not locked.
The last resort is to scan the document yourself into an accessible file.