If you go to manual.playstation.net/document you can read the full manual rather than the quick guide that comes in the box
For reference this is the bit you wanted:
Adjust settings for upscaled output when playing a DVD. Upscaling is a feature that can be used to enable content recorded at SD resolution (NTSC: 480p / 480i, PAL: 576p / 576i) to be displayed in HD resolution (1080p / 1080i / 720p). Because the video content of commercial DVDs is recorded in SD resolution, higher resolution video can be achieved by enabling upscaled output.
Off Set to disable upscaled output.
Double Scale* Set to upscale and display with double horizontal and vertical dimensions without changing the proportions.
Normal Set to upscale and display at a size that matches the screen size.
Full Screen Set to upscale and display at full screen by changing proportions and stretching the image
* This option can be used only when the video output setting of the PS3 system is set to 1080p or 1080i.
To use this feature, a TV that is compatible with HD input and output must be connected using an HDMI or component AV cable. Also, the video output setting of the PS3 system must be set to 1080p, 1080i, or 720p.
When playing copyright-protected DVD content such as commercially available DVD-Video, an HDMI cable is required to upscale the video content.
If image quality is reduced or the image does not look right when upscaled, set this option to [Off].