Why mixed image formats cause so much friction
Images arrive in whatever format the tool that produced them preferred. A screenshot on Android saves as PNG. A photo from a DSLR is JPG. A website’s downloaded hero image is often WebP. A exported chart from a design tool might be PNG with transparency, and an old scanned diagram could be a BMP.
Many portals accept only JPG, most document systems want PDF, and printing a folder of mixed images directly produces pages in whatever order the file manager happened to choose. Converting everything into one PDF normalises all of it: consistent page size, consistent order, one file to send.
Because this conversion happens in your browser, it is also the practical choice for design files, invoices, medical reports and anything else you would rather not hand to a third-party uploading service.
How transparency, colour and resolution are handled
PDF pages are opaque, so a transparent PNG placed on a page will show white behind it — which is almost always what you want for a logo or a chart. If you need the transparency preserved for editing later, keep the original PNG; a PDF is the wrong container for it.
Colour is preserved exactly. Images are embedded as JPEG at the quality you select, and the colour profile of the source is respected as far as the browser exposes it. For documents where colour accuracy is critical, such as product proofs, set quality to 100% and leave downscaling switched off.
Resolution follows the same logic as any print job. An image needs about 150 pixels per inch of printed page to look crisp. For an A4 page (8.3 inches wide) that means about 1250 pixels wide. A 4000-pixel phone photo has far more than it needs, which is why the optional downscale cap saves so much size without any visible change.
Real use cases people bring to this tool
Design handover: a folder of exported mockups becomes one PDF that a client can scroll through. Keep it on “page fits the image exactly” so each screen keeps its true proportions.
Receipts and bills: a month of screenshots from a payments app becomes one expense claim, in date order. Switch on downscaling to 2000 pixels to keep the email attachment modest.
Study notes: photos of the blackboard, a PNG diagram and a WebP chart from a website combine into a single revision file, in the order you actually want to read them.
Certificates and proofs: a PNG screenshot of a payment confirmation plus a JPG photo of a signed form makes a complete submission for a portal that only accepts one attachment.
Choosing between this tool and JPG to PDF
They share an engine and produce the same kind of output, so the choice is mostly about defaults and convenience. The JPG to PDF page is tuned for photographs: margins of 5 mm, portrait handling, and wording aimed at camera rolls.
This page is the generalist. It advertises support for five formats, defaults to no margin so screenshots and charts fill the page, and handles transparency and flat graphics sensibly.
If all your files are JPG photos, either page gives an identical result. If you have a mix — or you are not sure what format your files are — start here. And if your images are on an iPhone in HEIC format, the HEIC to PDF tool decodes Apple’s format first and then does exactly the same job.
Whatever page setup you choose, look at the result before you send it. Open the PDF, check that no image has been cropped unexpectedly, and confirm the pages read in the order you intended. Five seconds of checking saves the awkwardness of resending a document. Keep the original image files too: a PDF rebuilt at a smaller resolution is convenient to send, but the originals remain your best source if someone later asks for a higher-quality version of one page.