Compress image files
The large size of the picture in PowerPoint is also the main reason for the overall volume of the document, and the PowerPoint2002 and later versions can compress the image and remove unwanted data. Right-click the picture, and then click Format Picture on the shortcut menu. Click picture → compress. Under Options, select the Compress Pictures check box and the Delete Picture trim area check box. If prompted, click Apply in the Compress Pictures dialog box, and PowerPoint will automatically compress one or more pictures for you.
If you are using PowerPoint 2000 or earlier, click the picture you want to compress to select it. On the Edit menu, click Copy. Again, on the Edit menu, click Paste Selective. For most images, such as photos or scanned graphics, click JPG. For an image with a large area of single color, or an image that contains important text or a detailed picture, click PNG. Finally, delete the original image.
Working with embedded objects
These objects and images are easy to compress. If you have finished editing the image, you can right-click the image, point to Group on the shortcut menu, and then click Ungroup. Next, right-click the image again, point to Group on the shortcut menu, and then click Regroup. Ungroup discards OLE data and leaves only a picture of the format that PowerPoint can compress.
Also, copying and pasting images from one slide to another in PowerPoint can work. No matter how many times you use the image, PowerPoint stores only one copy of the image, so reusing the image can actually help you reduce the file size.
Embed only the fonts that you want
When you embed fonts in your presentation, your presentation may increase the size by the font file size. Before you decide to embed, check the size of the font file. Some new Unicode fonts have very large font files!
Turn off the Quick Save feature
Open a good speech with PowerPoint, click tools → options → save, and clear the Allow fast saves check box. When you turn off the Quick Save feature and save the speech document as a new document, the new document will be much smaller in size.