macOS: lossless PNG to PDF conversion
ImageMagic

You can use ImageMagick to convert your PNG images to PDFs.

convert -density 100 sample.png sample.pdf


See How can I convert a PNG to a PDF in high quality so it's not blurry or fuzzy? for a related question and answers over on the Unix &amp; Linux site.

Installing ImageMagick and convert

To install the free and open source ImageMagick, and the included convert tool, you can use the Homebrew project.

Once brew is installed, use the following command to install ImageMagick:

brew install imagemagick


Online Services

Alternatively, you can use a web service to perform the conversion for you. Search for convert png to pdf to find such services:


http://png2pdf.com
https://www.zamzar.com/convert/png-to-pdf
https://cloudconvert.com/png-to-pdf