Sago:
PM files cannot be flattened. A PM file is not a rastered page, it´s a
sequence of commands how to build a page. Empty paper consumes very
little space, let´s say 30kbytes for infrastructure.
a) Link all images, don´t embed.
b) Save better=smaller instead of faster (default). This deletes the history.
Then "Save as" doesn´t create considerably smaller files (a few percent).
c) Split into chapters and "book" them finally.
The speed for editing doesn´t depend on Link/Embed mode.
Can be increased only by low resolution graphics preview.
Best regards --Gernot Hoffmann