Check your printer's settings to make sure it doesnt have "fit size to page" or something like that selected. My 600dpi laser and my cheap 300dpi $50 bubblejet both print at the exact size, well as close as I can measure.
Any more info to share about SMD soldering?? I've always used a toaster oven, which does the job fine but I hate putting tiny boards back into a "murky cave" and the delays to open doors etc.
I've been thinking of changing to a electric frypan so I can get my face over the board to check and poke at it if needed, with good light, using the frypan for the main preheat 150'C and then using a modified heat gun blowing gently down on the pcb to lift the temp for the main melt. I think this will work better than the toaster oven and also allow many more options for just doing an area of a board, or for reworking. And should involve better heat control and less potential damage to parts.