PNG to PDF specifically matters more than it might seem, because PNG is the format most screenshots, scanned line art, and graphics with flat colors are saved in, and it is lossless by design. Nothing gets thrown away when a PNG is created in the first place, unlike a JPG, which discards some detail every time it is saved. Converting a PNG to PDF does not add any further loss on top of that. The image data going in is the image data that ends up embedded in the PDF page.
One thing worth knowing before you convert: PDF does not support transparency the same way PNG does. If your PNG has a transparent background, a logo exported without a solid background color, for example, that transparency gets flattened against a white page when it becomes a PDF. This is standard behavior for essentially every PNG to PDF converter, not a flaw specific to this one, but it catches people off guard if they are expecting the transparency to carry through. If you need the transparent version preserved, keep the original PNG file alongside the PDF rather than relying on the PDF to hold onto it.
PNG tends to produce a larger file than JPG for the same photo, since JPG's lossy compression is specifically tuned for photographic detail and PNG is not. For a photo, JPG is usually the more practical source. For a screenshot, a scanned form with sharp text, or a diagram with a handful of solid colors, PNG is usually the better source, since JPG's compression tends to introduce visible artifacts around sharp edges and text that PNG does not have in the first place. Converting either format to PDF preserves whatever quality the source image already had.
PNG shows up constantly in a specific set of situations: a folder of screenshots that need to become one document for a bug report or a client handoff, a set of app store or design mockups that need to go into a single PDF for review, or a scanned form saved as PNG by a scanner that defaults to it. In all of these cases the images are usually not photographs, they are graphics or text-heavy captures where PNG's lossless compression was the right choice to begin with, and carrying that quality through to the PDF is the whole point.
Order matters more than people expect when combining several PNGs into one document, the same as it does with any batch of images. Most file pickers select images in the order you click them, which works fine if you are careful, less so if you select a whole folder at once and the system sorts by filename or by date modified. If your screenshots or scans do not have an obvious naming order already, renaming them with a numeric prefix before uploading (screenshot-01.png, screenshot-02.png) is the most reliable way to avoid needing to fix the order after the fact, though the reorder arrows here handle it either way.
This works the same way on a phone as it does on a desktop. Open the page in your phone's browser, select PNGs straight from your camera roll or your screenshots folder, and the conversion runs identically to a laptop, with nothing to install on either device.
A single PNG converts just as well as a batch of thirty, and mixing PNG and JPG in the same conversion is fine, the tool does not care what format each individual page started as. If you want the fuller breakdown of what generally affects image quality during a conversion like this, this post covers it in more depth, most of it applies to PNG the same way it applies to JPG.
