Steam does delta compression automatically and for most changes shouldn't be an issue.
UE4 has an append mode to add extra content in separate .pak, but if you are using Steam to distribute it doesn't save you anything. I believe it understands pak files enough to decompress, delta encode, then recompress.
UE4 has an append mode to add extra content in separate .pak, but if you are using Steam to distribute it doesn't save you anything. I believe it understands pak files enough to decompress, delta encode, then recompress.