I have Altium 15 and 16, so I don't know if this was changed between 14 and 15/16. Still here is what I found:
1) The PDF output page size and oriƫntation
In the output job, on the right-hand side you have the PDF 'output container'.
- If you select it (click on it) you see "change" and "remove" in the top right corner of the selection.
- Click "Change"; a new window opens with the PDF settings
- Bottom right corner there are three buttons: Advanced, OK, Cancel. Click "Advanced"
- Bottom left of the settings is called "page size and orientation". For both the Schematic and PCB output you can select either to use the Source Document size and orientation, or whatever you select in the page setup dialog.
I have mine set to "Source Document" as I want my PDFs in that size. Also, if I remember correctly, when it comes to the page setup dialog, Altium looks at your printer driver and settings to determine which page sizes it presents. I have a printer that does A4 only. Still I like my PDFs at A3 or larger. That's why I bypassed the page setup dialog and setup my schematic templates at the size I want.
2) Output scaling
- In the output job, right click on your document and from the drop-down menu select "page setup" (second to last in my case)
- A new window opens. Top left in that window you have the "page setup dialog"-settings for page size and orientation.
- Top left you see the "Scaling". In my case it's set to "Fit document on page." for schematics and I use "Scale: 1.00" for PCB output.
Hope this helps