PGP Self Decrypting Archives file sizes are limited to 4GB. This is due to a size limitation for executable files in Windows.
A PGP Self-Decrypting Archive (SDA) is a PGP Zip Archive that can be opened on any Windows computer, even those that do not have PGP Desktop installed. PGP Zip SDA files are standard Windows executable (.exe) files that you an open simply by double-clicking them.
PGP Zip SDA files are slightly larger than regular PGP Zip Archive because the self-decrypting mechanism requires a certain amount of extra space (usually about 100 KB).