Home / Problem with display

First of all I really like SumatraPDF. It’s fast and lightweight.

Now the problem. I used SumatraPDF to open the following file:
https://link.springer.com/content/pdf/10.1007/s002220050049.pdf

I found that all the horizontal lines in the fractions do not show up. See for example the equation at the bottom of p. 2. I used Adobe Acrobat Pro to open the same file. What I found is that the lines show up but are very dim. However, Foxit reader displays the lines very well. I wonder what the problem is.

Unfortunately the generator of that extract is unclear, and its possible a converter was used to produce the file.
Equally the latest version (1.13) of MuPdf which is the render engine that SumatraPDF uses, cannot show those horizontal lines within the text area.
It may be worth raising this as an issue (bug) at https://bugs.ghostscript.com (ensure you report it as a MuPDF bug).
In cases such as this it may be useful to regenerate/convert the file as an image based pdf, however you would need to consider keeping a copy of the source file for text extraction etc.