I have a 1200×7200 pixels PNG, and I want to slice it into a multipage PDF, 8.5×11 inches, with 1 inch margins.

For convenice, here are the 8.5 and 11 inches in pixels:

Inches	Pixels, at 72 PPI	Pixels, at 300 PPI
8.5	612	2550
11	792	3300

I tried

# version 1
magick input.png -crop x3300 +repage -units PixelsPerInch -density 300 output.pdf

but it doesn’t leave margins.

Using trial and error, I came up to

# version 2
magick input.png -crop x2700 -repage 2550x3300+100+100 -units PixelsPerInch -density 300 output.pdf

but I cannot figure out why the text on the last page is moved to its bottom (to fix this, I tried to add -gravity center, but this remove margins).

I also don’t understand why, to create margins, the value 100 works for me. Since I use -units PixelsPerInch and -density 300, I assume that 1 inch will be 300 pixels and not 100, but changing -repage 2550x3300+100+100 to -repage 2550x3300+300+300 makes the margins extremaly large.