ArcReader is a free, easy-to-use desktop product that allows anyone to view, explore, and print maps created by ArcGIS Publisher.
Published Map Files (PMF) contain instructions about the location and symbology of data layers (rendering rules, scale dependencies, etc.) including geodatabase connectivity, Internet connections, and Geography Network layers.
No, ArcReader cannot author or modify the published maps. ArcGIS Publisher and ArcMap, (ArcView, ArcEditor or ArcInfo) are required to edit PMF files.
ArcGIS Publisher allows you to extract all the data needed for a map and package everything for easy distribution.
ArcGIS Publisher includes an ArcReader developer component for embedding ArcReader or creating custom applications for viewing Published Map Files.