When Frame imports a PDF, it converts it on the fly to EPS format (it does not modify the original file, however). This can add significant overhead to a CPU, so you happen to be using a system a bit short on horsepower, consider converting the PDF to EPS pages.
The default EPS level a file is converted to is Level 1. However, you can add a line to the ini that changes that level to 2 or 3:
where x = 1, 2, or 3.
Level 1: Dropped in early 90s, so there is not much point in using it. However, it might be of help if you find a certain page that crashes upon printing or PDF generation, although you will probably lose any color.
Level 2: Works on everything except the most ancient PostScript printers. Highly compatible with HP's clonescript printers.
Level 3: Not particularly compatible with HP's clonescript printers. If you're printing to a newer Level 3 Adobe device (which includes Acrobat Distiller 4 and higher), it will give you faster, smaller files.