Problem reading (18)

Microsoft and possibly Adobe have programmed their applications to (1.) prevent piracy, and (2.) sell more products.

If the file you want to open was authored with anoter application (eg.Illustrator)and you want to save it with Acrobat, both Illustrator and Acrobat must be present on the same computer.

Check my theory, by opening the PDF and saving it on a computer that has both applications installed.

If I'm wrong, please re-post this question.

This is not the source of the problem becuase this happens on the machine that originated both files. Illustrator is also an Adobe product, but now superceded by something else.

I was also concerned about possible font inconsistencies, but I checked that only one font (Arial) was present in the document.

Have you checked the security settings?
Was the file Enabled with Adobe Reader Usage Rights?
When fields were added, were they added with the originating application?
Do you have the latest updates for Acrobat 8.1?
Have you tried File > Save As (or Save A Copy, if Save As is not shown)?Hope this helps.

The security setings are all open and this occurred with Acrbat Professional 8.1, which was the application used to add the form fields to the original document.

Yes, the latest updates are installed. The system reports Acroobat Pro 8.1.0.

Yes, I've tried 'save as' which generates exactly the same error message.

I am deeply curious why Adobe should tell me that the error code is 18 but not provide any information about what that might mean.

I can't answer as to why it happens but my workaround is to 'Reduce File Size' and change the Reader Level then resave so whatever Reader Level you actually want. I've never seen or heard of a listing of the error numbers or what they mean...

HTH
Meabh