When proofing a document on the web, there are a few things to consider in order to review it with accuracy:
1. View the document at 100% scale. The reason for this is so you can get an accurate representation of the document itself, and review details such as font size, image clarity, and the text content itself. Depending on your computer's pdf viewer, command+1 or command+0 should re-size the display to 100% scale.
2. Do not proof the document on your phone. Mobile devices are unable to display pdf's correctly, and often result in very inaccurate colour representation. Often colours will appear much darker or much more vibrant than they actually are. Instead, please review proofs on your laptop or desktop whenever possible for the most accurate representation.