I'm here to provide a solution!!!!
The problem is that the PDF were published with edit / print permissions, and it has a owner password on the Form 80 (and other immigration forms).
When you open the PDF, you can see the PDF and make changes but the moment you save it, Preview resets the entire document permissions and you can no longer edit the document. You cannot export or print it either - this will again cause Preview to save the document and you won't be able to open the document again.
However, I've figured out a way around this... you'll have to use Chrome or Firefox (NOT Safari, which I guess uses the same PDF viewer under the hood). Edit the entire document in Chrome or Firefox. If you want to save your progress, "save" a copy to your computer. It will have all the changes that you have made, AND it won't be locked. You can save yourself a copy so you can refer back to it. I email it to myself so I always have a spare editable file. Do not do anything else with it except edit.
Once you have completed the document, you can't sign it since neither Firefox or Chrome have that functionality. This is where you:
- make a copy (copy paste) of the PDF - we will use this so that it will get locked, not the original file
- open up the new PDF
- use preview's print functionality and save as PDF again (this removes all the editable fields but also removes the password)
- then you can open up the new PDF you just made and annotate it with the signature
- AND this PDF will be under the 5mb limit
Done correctly, you will always be able to open up the original PDF with Firefox or Chrome (drag drop) to make any changes, then follow the above steps again to sign.
Hope this helps! Can't believe AusImmi still can't provide something that works.