Compress the pictures in a document
Follow these steps:
1. If you want to compress only one picture, select it. Otherwise, click one picture so that Word makes the Picture Tools section of the Ribbon available.
2. Under Picture Tools, on the Format tab, in the Adjust group, click Compress Pictures button:
3. Choose options in the Compress Pictures dialog box:
Compensation options group:
- If you want to compress only the picture you chose in step 1, select the Apply only to this picture check box. To compress all the pictures, leave this check box cleared.
- Select check box Delete Cropped Areas Of Pictures if you want Word to get rid of any parts you crop off pictures. If you clear this check box, Word merely hides the "cropped" parts. This hiding is good if you want to be able to restore the cropped parts, but it's bad for file size, and it may also have security implications (for example, a customer may be able to restore a part of a graphic that you had intended to crop off a document).
Target output group select the HD (330 ppi) option button, the Print (220 ppi) option button, the Web (150 ppi) option button, or the E-mail (96 ppi) option button to tell Word what picture quality you need (ppi is pixels per inch, and a higher number indicates higher quality). If you're not sure, use the Use document resolution setting - you can always reduce it later, but you can't restore information if you choose a lower setting.
4. Click the OK button. Word compresses the pictures in the document.
See also this tip in French: Comment compresser les images dans un document.