The earlier processing and format of the document doesn't affect the possibility of cryptanalysis if that processing is done in a way that leaks no information about the plaintext to an attacker.
That caveat is important. Compression side channels were the source of the CRIME and BREACH attacks on TLS. Attackers could trick browsers into compressing data they sent along with some data that should have been secret to the user. When the attacker-controlled data was equal to the user's secret data, the resulting compressed value would be smaller than if the two values differed. That let the attacker infer that their guess was correct, even if they couldn't read the (encrypted) compressed data.
There have been numerous other side-channel attacks on various security systems. Padding oracle attacks on RSA PKCS#1v1.5, the Spectre and Meltdown attacks on CPUs, Rowhammer against memory, etc.
Note that side-channel attacks don't actually break the cipher, they bypass it entirely. By analogy a thief doesn't have to cut (or pick) a bike lock if only the front wheel of the bike is locked to a rack, they can just remove the front wheel and take the (more valuable) remainder of the bike. They're sometimes still part of the general field of cryptanalysis, but they're different from algorithmic attacks.