So you've decided to preflight (which was smart!) and now you have a preflight report that shows a number of errors... It seems like your problems have only just begin...
Not quite though, you've identified what is wrong with that PDF file; that is very valuable information. At least you now have a chance to fix what is wrong, the file won't go further down the workflow and come around to haunt you later on! Let's see how you get some more information on what is wrong with your file and how you can fix it.
Preflight reports can be cryptic, and the first step in figuring out how to fix the errors in the file is understanding what they mean. For all errors that have to do with the PDF/X standard, you can download the "Ultimate Guide to PDF/X". It can (amongst other places) be downloaded from the IPA web site. It contains the typical errors you can get when you preflight a file against the PDF/X standard; explains what they mean and how you can go about fixing them.
In a similar fashion, all errors and warning message you can get during preflight using Enfocus technology are documented on line on the CertifiedPDF.net web site.
Typically those resources give you the choice of fixing the error in the PDF file you have, or explain how you have to fix it in the original application (after which you have to recreate the PDF file from the original application). Both approaches have their advantages and disadvantages...
Going Back to the Original Application
The advantage of going back to the original application is that it is usually easier to fix the problem. So much information about the document is lost when converting to PDF that it can be a bit of a challenge to make certain corrections in the PDF file. The other advantage is that your original native document stays up to date.
Of course it isn't always possible to go back; in some cases the original documents are no longer available. In other cases there just isn't time to go back to the creator of the file. And finally a number of problems simply aren't fixable in the original application; no matter how many times you go back to Microsoft Word, you're never going to get proper CMYK color out of it...
Fixing the PDF file
So fixing the PDF file is sometimes the only available option. Adobe Acrobat supports a limited amount of editing, and allows opening line-art and images in an associated editor (such as Adobe Illustrator or Adobe Photoshop) for editing.
For truly extensive editing, have a look Enfocus PitStop Professional. This plug-in allows fixing problems during preflight (correcting certain problems on the fly) and it also allows a vast array of manual and automated editing on any object in the PDF file.
Whatever arguments you favor, try to remain realistic. Chances are that sooner or later you'll find a use for both methods. So make sure you know what is possible; when the time comes you'll be grateful you do.
Enfocus has had its PDF editor since 1997 and the amount of people that walk up to us and say they think editing PDF files is a bad idea is really big. However, the amount of people that have to grudgingly admit they don't like it but did have to fix something is at least as big. Fair warning!
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.