What is compressed in each document type?

TypeMetadata CompressionZip CompressionLossless Image Compression
PDF (PDF/A)Supported
DOCXSupportedSupportedSupported
XLSXSupportedSupported
PPTXSupportedSupportedSupported
JPG (JPEG)SupportedSupported
PNGSupportedSupported

DOC refers to the older Microsoft Word format used after 1997, while DOCX refers to the newer XML-based format, used after 2007.