I've been using both Kindle DXG and DX (lower 7:1 contrast compared to 10:1 on DXG) for reading pdf/djvu/cbz books outdoors all these years.
But only because there was KPV reader (non-touch version of Koreader) with all the necessary pdf reading options available therein (many zooming/cropping options, font darkening, bookmarks, links, folders/subfolders etc.).
So, installing KPV is the first thing every owner of Kindle DX should do.
https://www.mobileread.com/forums/sh...&highlight=kpv
We can even normally read those demanding pdfs from archive.org site that are very slow to flip through on many lcd tablets/notebooks because of their compression method implemented, but we need to change pdf compression beforehand, either by simply creating a new pdf as exported uncompressed images (10 x bigger in MB size but a lot quicker to flip through), or by using Adobe Acrobat's Clearscan OCR mode for both a lot smaller pdf size and a lot quicker page flipping, or by using K2pdfopt app for DX's b/w screen resolution & size.