What is 100% zoom in a PDF?

[JJacome]

When I open a PDF and set it to 100% zoom, what exactly does that mean? 100% of what?

If I have a landscape letter size page, 100% zoom goes beyond the visible Reader window.  I am supposing this has something to do with document and screen resolution, but PDF Properties doesn't list a document's resolution, only it's size.
Related to this, if I want a document to open at 100% and give a specific size, say 1920 x 2400 pix, how would I go about achieving that?

Thanks.

[try67]

100% zoom means that 1 inch of the PDF page will appear on 1 inch of your screen.

[JJacome]

Thanks for the reply. But, an 11" wide document at 100% is displayed as 14.75" on screen. So that doesn't seem to be it.

[try67]

Then check the "Scale for screen resolution" setting under the application's Preferences, in the General tab.

[JJacome]

Thanks. Changing from the current setting of Auto-Detect to No Scaling does change the 100% size down to 11_7/8", but still not 11".
By trial and error, it seems the 100% zoom level doesn't depend on the resolution at which the PDF was published. Any resolution gives the same 100% screen size for the same paper size. But 100% screen size does depend on PDF paper size. At a larger paper size of the same content, 100% gives a larger view size for the same object, ie. a higher real zoom level. In other words, an object printed on Letter size appears smaller at 100% than if the same object is printed on Tabloid. Which does show - as you say - a relation between paper dimension and screen dimension at 100%. It just doesn't seem to be one-on-one.

[try67]

It is for me... Maybe there's some other scaling going on in your machine.

[try67]

PS. I don't have a "No Scaling" option in this setting. I have "Auto Detect", "100%", "200%" and "System"...