Crop PDF pages

No. Cropping sets the page box a reader is shown; the ink outside it stays in the file and stays selectable. That is what makes it reversible — set the box back and the whole page returns. If you need content genuinely gone, use Whiteout in the editor: it is a redaction, and what it covers is removed from the file rather than hidden under a rectangle.

Yes. Switch to Each page and the box you draw belongs to the page you are on; step through with the arrows and give each one its own. Pages you never touch are not cropped at all. On All pages the single box goes on the whole document, or on the pages you name in the Pages field — a list like 1,3,5-8.

The crop is kept as a share of each page rather than as a fixed rectangle, so taking a fifth off the top takes a fifth off every page whatever size it is.

Yes. It is stored as the page CropBox, which every reader and printer honours. Some professional print workflows deliberately look past it at the full sheet.

No. The whole crop happens in this browser tab and the file never leaves your device.

Not to a fixed target size — cropping trims margins as a share of each page's existing size rather than resizing it to a dimension like A4 or Letter. If the page itself needs resizing rather than trimming, this is not the right tool for that.

Yes. Drag the crop box with a finger the same way you would with a mouse, or type the margins instead if that is easier on a small screen. The file stays on your device there too.