The "image" that you see is made up of 144 sub images, and there is not overlap of these images. The issue is that this leaves the rendering engine work to make sure that there are no thin line gaps between the images.
Most browsers handle this but not IE/Edge. Can your users switch to FireFox/Chrome/Safari?
Ideally this is resolved at the time of PDF generation, so that the images have an overlap of some pixels, or simply merge the image into one (compression works better that way anyway).
Another work around is to have PDFNet flatten the page so that it is just one image. I would not recommend as a general solution, but you could "repair" this one file for example.
Is this the only document you have encountered like this?
Who generated the file, you or one of your users?