How to determine and alter dpi of a PDF?

The PDF was created from 70 JPGs scanned at 150 dpi. 

Since there as no way to convert the PDF to 200+ dpi, I had to take the 70 JPGs that made from the scanner. 

1. I opened each of the 70 JPGs with Microsoft's free Photo Editor *

2. select File Properties to convert them from 150 dbi to 200 dpi

3. Resave them as 200 dpi.

4. Then I recombined the 70 JPGs into a new PDF.

It worked. Acrobat's Paper Capture processed all the 200 dpi pages.

Indeed, as an experiment I left 2 JPGs as 150 dpi, and Adobe Acrobat stopped on those 2 pages and gave the message that it could not run Paper Capture on them.

Thanks for your reply which sent me in the right direction.

If there is a faster way than the above steps, let me know.

However, I see why Adobe insists on at least 200 dpi original scanning.  The 150 dpi saved as 200 dpi JPGs did not get recognized well by Adobe - with many character errors.  Lighter typed sections were not picked up at all.  Google would not be able to pick up much from it, but a lot of garbled words (assuming they require 200 dpi too - anyone know?) 

So I will have to go back to the scanner and rescan all 70 pages at 200 dpi , then make a new PDF to be fully readable by Adobe Acrobat.

In the mean time, to get the text OCR scanned quickly, I used PDFOCR from www.pdfocr.net which recognized the characters on the 150 dpi pages very well.

Lesson: Always scan text documents at least at 200 dpi.

* This process was made less tedious thanks to Aldo's Macro Recorder from www.AldosTools.org

Document is at www.CICorp.com/TM/Research/CTOMEEG