When comparing PDF Bob vs Sumatra PDF, the Slant community recommends Sumatra PDF for most people. In the question“What are the best PDF viewers for Windows?” Sumatra PDF is ranked 1st while PDF Bob is ranked 19th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Supports addition of comments to PDF in "Annotate" mode
Pro Supports addition of the images to PDF in "Edit" mode
Pro Support password protection of the edited files
Pro Supports the addition of rectangle, circle, line and arrow in both Edit and Annotate modes
Pro Stores the files online if you have an account
Pro Can export files in PDF, DOC, DOCX, JPG and PNG formats
Pro Starts quickly
Pro Free and open source
Sumatra is available for free, licensed under GPL with source code available on GitHub.
Pro Low resource usage
Pro Does not have heavy editor features
Annotations and other heavy features are just not needed in reader.
Pro Extensive keyboard shortcuts
Pro Elegant interface
Pro Portable
The application consists of a single file that can be run without installation. You can put it on an external device, such as an usb thumb stick and run it on any Windows machine from the thumb stick.
Pro Multilingual
It's available in 69 languages.
Cons
Con No "Sign PDF" tool
Con Windows only
Con Lacking in features
Sumatra aims for simplicity at the expense of functionality. For example, there's no way to annotate PDFs or edit them.
Con Fonts are not smooth enough
Not as smooth as e.g. Adobe Reader. No anti-aliasing
Con Cannot crop empty fields
Just got used to this killing feature on Goodreader on Mac.