I did get the other samples you sent, and as I see it, the document is simply a very poor scan. I notice that even on the desktop, if I view it at 100% zoom the artifacts you mention are present. However, the desktop defaults to zooming this document to 150% (on my monitor) where it looks better. If I zoom the document on the mobile Reader, I see similar improvements. Further, when I view the document on a Retina (higher resolution) iPad or iPhone, again I see improvement. It seems that this scan requires higher resolution to look "ok". This is partially due to the sampling method we used for compressed images that we use at this resolution. This is a tradeoff that we've intentionally made for performance and works generally with most documents and images, but happens to fall short on this particular PDF at 100%.