Why not just try every permutation of (1,l)? Let’s see, 76 pages, approx 69 lines per page, say there’s one instance of [1l] per line, that’s only… uh… 2^5244 possibilities…

Hmm. Anyone got some spare CPU time?

It should be much easier than that. You should should be able to serially test if each edit decodes to a sane PDF structure, reducing the cost similar to how you can crack passwords when the server doesn't use a constant-time memcmp. Are PDFs typically compressed by default? If so that makes it even easier given built-in checksums. But it's just not something you can do by throwing data at existing tools. You'll need to build a testing harness with instrumentation deep in the bowels of the decoders. This kind of work is the polar opposite of what AI code generators or naive scripting can accomplish.

Easy, just start a crypto currency (Epsteincoin?) based on solving these base64 scans and you'll have all the compute you could ever want just lining up