I created this 200x200px box in AI file (72ppi):
After saving it as PDF, the PDF opens in different resolutions on different apps.
Here it opens as 305x305px in Adobe Reader:
Here it opens as 268x268px in Google Chrome:
What's happening here? I wanted to do a web presentation in the popular 1920x1080px, but I noticed, that the 100% didn't fit the 1920x1080px screen in any application.
EDIT: I used LightShot printscreening tool to estimate the dimensions of the box.