[Feature request] Crop page(s)

When this feature selected by user, then PDF file should be OPENED TO BECOME VIEWABLE TO USER WITHIN SAME PROGRAM to make user able to see what areas will be outside crop box (the user should be able to brows pages of PDF & navigate between them). User should be able to select page range to apply cropping process as desicribed above:

• crop all pages
• crop odd pages
• crop even pages
• crop ..........

Also user should have ability to custom margins that will be outside crop area (& here the scale rubbers vertical & horizontal will be helpful or you can add at lower boarder of UI on left side opposite to "Generate PDF" that is on right corner, add on left corner something like this (W:....,L:....) where W: is width while L: is length. It is nice to allow units optional either in mm, or cm, or inch, or ppp (point per pixel)