[tanto]

When I open PDFs I often want to edit the filename to adjust it to the content. SumatraPDF is awesome and opposed to Adobe Reader and other PDF readers it does not take an exclusive lock on the PDF file so you can edit its filename. The fact that it is extremely fast is another big benefit.

[Semaphor]

I sometimes work with Paged Media CSS, I’ll often need to generate a file multiple times after editing the CSS to see if it accomplished what I wanted. With Sumatra PDF it instantly updates the file when the new version is generated, it’s awesome.