Enlarge a PAM image by duplicating pixels. See also:
pbmreduce,pamditherbw,pbmpscale. More information: https://netpbm.sourceforge.net/doc/pamenlarge.html.
pamenlarge {{[-s|-scale]}} {{n}} {{path/to/image.pam}} > {{path/to/output.pam}}
pamenlarge {{[-x|-xscale]}} {{xn}} {{[-y|-yscale]}} {{yn}} {{path/to/image.pam}} > {{path/to/output.pam}}