I have several pages imported from scanner in PNG format. I use image editor to clean some noise, downscale to 100PDI, convert image palette to grayscale, etc. Finally I've got a bunch of PNG images of small size, looking good at computer screen still.
Then I need to save these PNG pages to a single PDF file for distribution. Earlier I was able to achieve this using Preview.app. However in macOS X High Sierra 10.13 this approach does not work any longer because Preview.app is trying to downscale PNG images by 30% to fit page size. After this transform the image is not sharp enough any longer.
In earlier versions of macOS X Preview.app generated PDF file without transforming the images.
Is there a way to make a PDF file from a set of PNG images using these images as-is (without any transformation)?