To specify the media size
In Power PDF, select File > Print, choose Kofax PDF as the printer and click Imposition in the bottom left of the Print dialog box.
Click the Media tab.
Check Autosize Media to print the imposition file to a medium which best fits the page size, or check Fit to media size to print the file to a medium that you specify as follows:
Select a standardized medium (A0 through A4, B4, B5, Executive, Ledger, Legal, Letter, Screen, Tabloid) or a custom media, if any. Custom media can be edited or removed.
Click Add to specify and add a custom medium. In the Custom Media dialog box, name the medium and define its width and height. Click OK to add this custom medium to the Media list.
Select Auto Rotate to allow rotation of the imposition file pages if that lets them better fit the selected size.
To place the page content onto a medium
In the Media tab, check Fit to media size, and specify a medium.
In the Margin group, set margins (left, right, top and bottom) for the medium (align page edge with medium sheet edge) when printed.
Set Horizontal and Vertical Scaling for the page content.
Click the Options tab and select Scale Larger Pages to ensure all pages of the original PDF document have the same size on a medium sheet. If the original PDF pages are of different sizes, all of them will be adjusted to fit to the first page when printed.