Why are Epstein’s emails full of equals signs?

Many of the emails released by the Department of Justice from its investigation into Jeffrey Epstein are full of garbled symbols like:

Or:

The scrambled text is so ubiquitous that it's spurred conspiracy theories that it could be some kind of code. But as believable as it might be that a cabal of elite sex traffickers would communicate in a secret language, the reality is probably more boring: The symbols are likely artifacts from the way the Department of Justice converted the emails to PDFs.