Altium design printing to pdf
I have had this problem a number of times. I discovered that the most reliable method for me was to print through the "Preview" panel within the OutJob. Steps are below:


If you haven't already, add an OutJob file to your project by right-clicking it in the Projects pane, selecting "Add New To Project", and choosing "Output Job File"
Under "Documentation Outputs" click "Add New Documentation Output" and select "PCB Prints" -> "[PCB Document]".
Right-click the "PCB Prints" line that just appeared and select "Configure" to set up which layers you want to print (I'm assuming you already know how to do this). Click OK to close the window.
Right-click the "PCB Prints" line again and this time click "Page Setup"
Select your paper size, orientation, and under "Scaling" change the dropdown to "Scaled Print". Set the scale to "1.00".


Up to this point I'm guessing you probably already did all this, but here's the difference:


Instead of clicking "Close" or "Print", click "Preview", and then click "Print" from within the "Preview" window. 


Printing straight from the OutJob never seems to work for me and I get exactly what you did (a print that doesn't match the PCB dimensions). Printing through the preview pane, however, does seem to do the trick.