The PNG to PDF converter passes an upright PNG's original bytes straight to PDFKit, so the image is not re-encoded before embedding.
Adobe's own PNG-to-PDF converter is marketed as a high-quality PNG to PDF conversion tool. Convert PNG images to PDF files for free | Acrobat - Adobe
PNG To PDFPreserving Quality So PNG To PDF Never Ends Up Losing Detail
When page size is set to Fit, the output page is created using the original image's pixel width and height instead of scaling it to a fixed paper size.
Add the PNG image with a transparent background to the upload area.
Select the Fit option for page size.
Checking Transparency and Fidelity
Save the converted PDF from the results panel to your device.
Open the PDF.
Compare the downloaded PDF against the original PNG for color accuracy.
Resetting for Additional Files
A start-over control appears once the PDF downloads, clearing the upload area so the next PNG can be checked for transparency without a page reload.
Press the start-over control beneath the download button to clear the transparency check.
Continue with Combine Multiple PNG Into One PDF or PNG to PDF Page Size, Margins, and Orientation.
Frequently Asked Questions about PNG to PDF Without Losing Quality
How do I preserve the original dimensions?
Choose Fit from the page size dropdown so the PDF page matches the image's pixel dimensions exactly.
Where do I find the reset option?
Locate the reset control directly under the results panel after downloading.
How do I check the transparency?
Zoom into the corners of the exported page and look for a checkerboard or solid fill instead of see-through pixels.
How do I start with a new file?
Add a different PNG image to the upload area after clicking start-over.