It’s quite a hassle when you have to send a large PowerPoint or word file via email. Normally the servers or networks will be configured to ensure the maximum size doesn’t exceed 4 – 10 MB. Zipping a file, in such a situation reduces the size of the file/files which does help you to an extent.
Zipping is a good solution, but the better approach is to use an application called PPTMinimizer which lets the user compress the files without changing the format.. up to 98% of their initial size is maintained.
Another approach is to create PowerPoint files in the .pptx, .pptm, .ppsx, ..ppsm, .potx and .potm format with any version of Microsoft PowerPoint 97 to 2007, which also helps in optimizing.
StarOffice or OpenOffice files saved in Microsoft PowerPoint format can also be optimized.
PPTminimizer is for those who love to speed up the loading time and save excess usage of disk space in mailboxes, servers and/or networks .
FOR very big files u can also use FFSJ a best tool for file splitiing and thereafter rejoining.
You could also try NXPowerLite which seems to give slightly better results and not damage the files.
There’s a 20-use free trial available here: http://www.neuxpower.com/products/nxpowerlite-desktop/solutions/compress-powerpoint/