[bazza]

I've just connected my tablet to Companion, opened a file (a single page with a tune): just below the right-hand corner of the notated tune there are two boxes - 'Restore crop' and 'Auto-crop'.  By clicking on 'Auto-crop', the image is enlarged to fit the screen area. 

I have also found it possible to crop images on the tablet without using Companion, by tapping the centre of the screen to bring up a number of icons.  Tapping the second one at the bottom left (square containing two small triangles) brings up a list of various functions, the first of which is 'Crop'.  As with the Companion process, tapping this enlarges the image.