To compress a single image

Using the Select Objects tool , select a pixel image.
Choose Window > Show Enfocus Inspector, and then click the Image > Compress category.
Select a compression method: JPEG or ZIP.
If you selected JPEG compression, select a quality level.
The higher the quality level, the more detail in the image will be preserved but the larger the size of your PDF file will be.
If necessary, select an ASCII filter.
Click Apply.