if you want a bigger printed schematic, it's best to upscale and change the image size in a graphics program like gimp, photoshop, or similar and also start with the highest resolution scan you can find. Upscaling will create more pixels and smooth things at the expense of a larger file size.

the images files on bingo.cdyn.com are all 300 DPI saved in the lossless png format. A pdf is typically downscaled to as little as 72 DPI and jpeg compressed. It will look badly pixelated with halo artifacts when printed at actual size and even worse if printed enlarged.

if you print an schem from bingo.cdyn.com and it came out badly, let me know and I'll find out why. Could be something wrong with the image parameters.