I've created a montage of photos on a background consisting of another photo in Word 2010. I definitely selected an A4 landscape template to create the document. However, on printing the document came out printed edge to edge side to side ie 297mm but top to bottom the picture is only about 160mm rather than the full 210mm. In effect, there's a white border on the top and bottom of the landscape sheet.
On checking in print preview, it shows that it will print just as it has done. I can't understand how it'd done this given that I filled a known A4 template with photos top to bottom and side to side..
Not sure about this as it should show correctly in the document editing view but it may be the margin setup.
Go to the menu "Page Layout -> Margins -> Custom Margins" and make sure Top, Bottom, Left and Right are set to zero. Click the "Layout" tab and set Header and Footer to zero. Click OK.
Also, your printer may not be able to print edge to edge on all sides, some do though.