1. The aspect ratio of a native Smath sheet is ~ 1.316 [Height/Width] For a full page image, attempt to capure the image in that ratio to avoid distorsion once the image is stretched in background. 2. To insert background, browse from file where saved, double click. 3. From a blank page [or that very document]: Insert Image from Menu, brush over, from Menu compose your background color, capture in the ratio 1 width, 1.33 height [that should do]. 4. Crop that captured rectangle, save as *.PNG in your file system.

This model background work sheet behaves Smath wise like if there is no background. You can background any region at will as usual. White background is [254, 254, 254]. Once the project done: make a PDF ... 1/1 original Smath document.