PDF-XChange Viewer does it
Very poor show on my part taking a year and three months to come back and thank everyone for their suggestions!
In the end I went for PDF-XChange Editor
, which is the replacement for PDF-XChange Viewer
suggested by Oldjim
above (though the older bit of software remains available).
The makers say of the newer bit of software...
Around 85% of the features require no license to use.
Approx 15% of the advanced features which are clearly identified will place a trial watermark on output if used without a license.
The thing I use it for is not one of the advance features, i.e. no watermark / no need to pay for a licence.
So thanks Oldjim and everyone else!