I have Affinity Designer and Photo for Mac desktop, and I'm a newbie to both. I tried importing a PDF (attached) that I need to edit into both Designer and Photo. In both programs the PDF is layered, which is great since that means I can edit it easily. However, the topographic map layer becomes very pixelated. If I do my edits and then export as a PDF or PNG (or any file type that I've tried), the topographic map layer remains pixelated. This layer looks smooth when I open the PDF in a viewer. It is also smooth and not pixelated when I open the PDF using Photoshop (I don't have Illustrator). However, in Photoshop the PDF doesn't open with layers.
Years ago I know that my partner managed to do some basic edits to this PDF without any pixelation, I believe with Inkscape, so it should be possible. Can someone let me know what I'm doing wrong in Affinity?