Based on the work in https://tex.stackexchange.com/a/18776

Usage

Place your pdf in the same folder as the two scripts and rename it Script.pdf
Run sh ./findlines.sh Script to generate the files for NumberPDF.tex

Variables

Edit the following in NumberPDF.tex to customize your numbering:
\numpages=62 The total number of pages in the PDF.
\numberby=2 Count by 2s, or whatever number you'd like.
\startnumbering=2 Start numbering after n lines. Useful for skipping headers in pdfs.
\offset=10 Offset of numbers from left margin. Useful numbers are in the range of 0-20ish.

Requirements

Requires ImageMagick commandline tools, and LaTeX