You can add video from your iPhoto or Aperture library or from your Movies folder, and set Pages to automatically optimize movies for iOS. You can also add audio from iTunes to your document.
Note: Audio and video files must be in a format that QuickTime supports on your Mac or device. If you can’t add or play an audio file or a video file, try using iMovie, QuickTime Player, or Compressor to convert the file to a QuickTime file, in MPEG-4 audio or H.264 video format.
Do any of the following:
Click 
in the toolbar, select Photos, Music, or Movies, then drag the file to place it anywhere on the page, or to a placeholder.
You can click the magnifying glass to search for media.
Drag a media file from your computer to anywhere on the page, or to a media placeholder.
Select the audio or video file on the page.
Click the Movie or Audio tab at the top of the sidebar on the right.
If you don’t see the sidebar, or it doesn’t have a Movie or Audio tab, click 
in the toolbar.
Drag the Volume slider to adjust the playback volume.
Click the disclosure triangle next to Edit Audio or Edit Movie, then drag the Trim slider to change the length of the audio or video.
Click the Repeat pop-up menu and choose an option:
None: Media plays one time, then stops.
Loop: Media plays continuously on the page until you move to the next page.
Loop Back and Forth: Media plays forward, then plays backward. The media continues to play forward and backward until the page changes.
You can set a preference in Pages to automatically convert movies in your document to H.264 (720 p) so they play on iOS devices.
Choose Pages > Preferences (from the Pages menu at the top of your screen).
Click General at the top of the preferences window, then select the checkbox next to “Optimize movies for iOS.”