Who may witness your document
The class of people who may witness your document is set by the law the document is made under, and the classes are not uniform. Choosing someone outside the class is one of the few defects that cannot be argued around.
There is no single national list of people who can witness an Australian document. Each Act defines its own class, and they differ considerably. The Commonwealth list runs to well over a hundred occupations. Queensland's is short. Some classes apply to affidavits but not declarations within the same state.
Justices of the Peace do the overwhelming majority of this work in Australia, and they do it as volunteers, without payment, frequently for decades. For most documents a JP is entirely sufficient, entirely free, and the right answer - the state registers and scheduled signing services are linked throughout this section for exactly that reason.
Where a legal practitioner is useful is narrower than it is sometimes made to sound. An Australian legal practitioner falls within the authorised class in every Australian jurisdiction, which removes any question about whether the witness was eligible. And a practitioner can be available at eleven at night, from a hospital, from a mine site, or on a Sunday, which a signing service at a library counter cannot. That is a difference of availability, not of authority.
These articles set out the eligibility matrix by document type and jurisdiction, explain the distinct roles of JPs, legal practitioners, notaries and Commissioners for Declarations, and answer the occupation-by-occupation question directly: can a pharmacist, a police officer, an accountant witness this?
The law where your document is made
Which law your document is made under decides its form, who may witness it, and whether it can be witnessed by video link.
Need a document witnessed?
An Australian legal practitioner, on a video call, in about ten minutes. Evenings and weekends included.