an important PDF has locked itself and I cannot get it open

Hi brains trust,

I recently sent a document to a colleague to fill out on my behalf, as they are nomintating me for a new visa in Australia. The PDF document has been sent back to me and upon receiving is locked.  Now the colleague can no longer open it, nor can I.  When I click on the PDF it says it is protected and to please use an open password. I have literally spent all day trying to get it unlocked / open to no avail. I never put a password on the document, nor did my colleague. I have additionally contacted immigration to see if they put any sort of password protect on this form 1000 and they do not. I am at a total loss. Last resort is asking my colleague to do this form again as it is a large undertaking and they are extremely busy. I am so frustrated and don't know what to do, please help!