This would be a fun little home project, however I don't know much about printers and scanners. This is stepping into an entire field and I'm assuming we have little background in compression, printing, scanning.
From a programmers perspective, one simple way to do this would be to use a palette of 255 colors + blank (to represent a 0 byte). Using this you can represent each byte using a single spec of color, rather than drawing each bit individually. With this you could read a binary file and create an image.
From paper you would scan the image into a known format (bmp?), Read the image and convert each color back to its respective binary byte.
You could go further to add a header to the data so a date, name, etc could be added and read back using the same color system.
I believe a 720k disk contains 737,280 bytes, With this system a 720k disk would require 737,280 colored markings. How small these marks can be is a future topic depending on printer and scanner ability to distinctly write and scan back 256 colors (including blank, white). I believe printers are only actually capable of printing maybe 16 or 8 colors at most per dot, they likely mix colors to create the overall effect of a final color. So I would not expect this method to work on the scale of a single dot.
Alternative ideas to consider would be using the 16 colors available to represent each possible nibble (half byte) and printing 2 dots per byte, possibly resulting in smaller overall prints compared to the 255 color method.. or 8 colors to represent 3 bits at a time.. and so on..use your imagination. You could also use more than one page per file obviously.
Yes its silly for real use but hey, fun project is fun..
Note: use a compression algorithm on the contents of the disk first to shrink it down before converting, thatll save space.. so using the full 720k would be a worst case scenario.
Sup. I like computers. Are you a computer?