I took a look at it.
I don't have a lock icon on the toolbar, but it is a scanned PDF. I understand that marking is not possible.
Is there a solution to work around this? What can you recommend?
Thx in advance.
You would need Optical Character Recognition (OCR) software to convert a scanned PDF to an editable or searchable PDF.
Unfortunately, free mobile or desktop Reader apps do not offer the OCR capability.
Adobe Acrobat DC (paid desktop app) supports it. You may want to start free trial to see if it meets your needs.
Here's the Adobe user forum for Scan & OCR with Acrobat DC: Scanning & OCR
Hope this helps.
Edit PDF tool , Highlight tool and Enhance scan tool are some options that can help you with similar needs.
Can you please share what exactly you want to do. So that we can share exact steps.