Because every single goddamn time

Command line: How do you rotate a PDF file 90 degrees? - Unix & Linux Stack Exchange

pdftk input.pdf cat 1-endwest output output.pdf

1- is needed because page range, here for all pages.

endwest etc from man page:

 [<begin page number>[-<end page number>[<qualifier>]]][<page rotation>]

The qualifier can be even or odd, and the page rotation can be north, south, east, west, left, right, or down.
Each option sets the page rotation as follows (in degrees): north: 0, east: 90, south: 180, west: 270, left: -90, right: +90, down: +180. left, right, and down make relative adjustments to a page’s rotation.