I'm in the process of producing QR-codes for use on product packaging. The codes are generated in batch and the resulting files are typically 25x25 px PNG files. Of course, such a small image would normally be way too low res to use in print, i.e. a 1x1 inch image would need to be 300x300 px in order to print in 300 DPI.
When it comes to simple images such as QR-codes (I guess this would also apply to bar codes without the digits) I realized that the actual resolution of the image is not really relevant, as I can easily resize the image to any size I prefer using nearest-neighbor resizing option in Photoshop. In a way, the resulting 250x250 px image won't contain any more information in terms of "QR pixels" than the 25x25 px version, apart from the obvious fact that the file will be larger in size. Also, when resizing to a width not evenly divisible by 25 (e.g. 70x70) the resulting QR pixels will not all be the exact same width.
This has got me thinking I can simply place the 25x25 px PNG in my InDesign layout, which will in turn be exported to PDF and sent to print. This seems to work out fine when I print the file on my printer, but on screen the image sometimes looks blurred (as you would expect with it being magnified). I have found that the blurring effect stems from the anti-aliasing setting in my PDF viewer, so there is obviously no information about resizing/anti-aliasing embedded in the PDF file, while the printer will resize the image without anti-aliasing (i.e. using nearest neighbor).
Finally, the question: Is there any obvious downside to using this method? Is it safe to assume that the 25x25 px image in my PDF document will be upscaled without anti-aliasing when I send it to the printing office? Would I be better of just manually upscaling it or converting it to a true vector format?
Bonus question: is there a better term for what I am referring to as vector-like in the title/question, that is the concept of a bitmap/raster image being upscaled without loss of quality?