I'm Adobe Acrobat 9 to merge a number of jpg files into one pdf.

Trying to figure out what determines the display size of the final pdf file.

I have one set of jpgs that are 682x1000 pixels at 72p/inch resolution - the height of the jpg pretty well fills my monitor screen vertically - it.s a 1920 X 1080 monitor.
When I use Acrobat 9 to convert that set to a pdf file, the pdf file displays at pretty much the same size as the individual jpgs.

Then I have another set of jpgs, pretty much the same size as the others - 707x1000 pixels but at 300 p/inch resolution. When I do that same conversion to a pdf file, the display size on the monitor is only about one-third as large as the first one.

I'm trying to figure out why - or better, how can I convert the second set of jpgs to be the same display size as the first set, not a tiny pdf.

I checked the View option to make sure I'm looking at "actual size" in each case, I changed the 300 p/inch to 72 p/inch in the second jpg set, I tried different options in Acrobat - all with no change to the final pdf file.
All changing the resolution did is to make the final pdf file more fuzzy.

I expect the "fix" is simple - but what is it - any Acrobat experts in the group?

Did you check under properties - what are your "initial view" settings?

Sorry, I lost you.

What "properties" did you want me to check. And what is an "initial view" setting.
Two totally new things to me on OS X.

I just checked the dimensions of both the jpgs and the final pdf files using 'Get Info'
For the first set, the jpgs are 682x1000 and so is the pft file
For the second set the jpgs are 707x1000 and the pdf file shows as 169x240

So what I see on the screen matches what 'Get Info' tells me but why is the second pdf so tiny?
It has to do with the resolution of the original jpgs I would think

Turns out it was the resolution.............

I changed the resolution of each jpeg from 300 to 72 pixels/inch, that gave me a resulting pdf which was the same display size on the monitor as the original jpgs.
And the reason this didn't work the first time I tried it - before even posting on ehMac, was that the Mac wasn't smart enough (or too smart) to recognize that the resolution of the jpg was changed but not the file name.
Normally, if I modify a file but keep the same file name, the system recognizes it and one gets a message asking if one wants to replace the existing file with the new file.
Changing the resolution in a jpg I guess is not enough of a change for the system to recognize, so it assumes it's the same file that already exists and the change in resolution is never made.