I had an interesting question about Live Preflight in Adobe InDesign CS4 from one of my Facebook friends today (an InDesign user from Italy).
But before I start, did you know that, according to an independent study, finding and fixing an error in an InDesign CS4 layout is 200% faster than finding and fixing the same errors using the Preflight options in InDesign CS3? The cool thing about Live Preflight in CS4 is that it alerts you of potential production problems in real time so you can quickly navigate to the problem itself and fix it. Like I always say, this totally beats the nasty phone call from your printer on a Friday evenening, just as you are leaving the office: "oh er hello Mr. Rufus, could you send that PDF again? There are some images in low resolution, and you are using more spot colors than you were quoted you for... Oh, and we need it now". No more!

Now you have a Guardian Angel looking over your shoulder, as you are working and being creative, whether you are laying out a document for print, flash, or the web.
Live Preflight is turned on by default for all new documents, and it uses a profile called Basic, which simply checks for missing or modified links, missing fonts, and overset text frames. If any of these conditions exist, the total number of errors in the document appears to the right of a red circle in the document window’s status bar [see image above]. Just open the Preflight Panel, look at the list of culprits, follow the hyperlink to the error itself, and correct it; it's as easy as that.
I've been a graphic designer for 20 years now, and this new feature truly rock the house!
What is incredibly useful about the profiles you create is that you can share them with your colleagues, so that everyone in your workflow respects a standard you have defined. You can also choose to embed the profile in the document itself, so that it travels with it as it moves from one layout artist to the other. Live Preflight is really a foolproof system for keeping your prepress sanity.

These are the potential errors that you can set Live Preflight to alert you about:
General
If you are going to share your profile with others, or just want to perform good house keeping, it is really meaningful to give the profile a short description.
Links
• Missing or modified links
• OPI Links (at this point, I am curious to know how many of you still depend on OPI workflows, and why)
Color
• If the required transparency blending space (CMYK or RGB) is not being applied
• If Cyan, Magenta or Yellow Plates are not allowed, and are present; for when you want to be sure that you are effectively producing a 1 color black (or a document with only spot colors)
• If color spaces and modes such as RGB, CMYK, Gray, Lab, Spot Color are not allowed, and are present
• Check the spot color setup of the document: a) limit the maximum number spot colors that are allowed, b) or if the predefined spot color must use Lab values or CMYK equivalents
• Alert of overprinting applied in InDesign
• Alert of overprinting applied to White or [Paper] color
• Alert if color [Registration] has been applied
Images and Objects
• Image resolution (Color image minimum/maximum resolution; Grayscale image minimum/maximum resolution; 1-bit image minimum/maximum resolution)
• If non-proportional scaling has been applied to a placed object (now this rocks!)
• Objects that use transparency
• Alert if ICC profile setting may cause CMYK conversion, or if there are any profile override (with the possibility to exclude images with no embedded profile)
• Layer visibility overrides
• Minimum stroke weight (with the option to also limit the check to strokes with multiple inks or white)
• Interactive elements
• Bleed and trim hazards (with the option to check for objects near the spine)
Text
• Overset text
• Paragraph style and Character Style overrides (with the option to ignore font style overrides / kerning and tracking overrides / language overrides / color overrides)
• Missing fonts
• Missing Glyphs
• Errors detected by Dynamic Spelling
• Font Types that are not allowed (Protected fonts / Bitmap / OpenType CFF / OpenType CFF CID / OpenType TT / TrueType / Type 1 Multiple Master / Type 1 / Type 1 CID / ATC [Adobe Type Composer])
• Non-proportional type scaling (this should always be checked, don't you know that you should never, ever scale type?)
• Minimum Type Size (with the option to limit the check to text with multiple inks or white)
• Out of date cross-references or cross-references that are unresolved (another great new feature in InDesign CS4 are Cross-References)
• Conditional text indicators that will print (yet another great feature in InDesign CS4)
Document
• If page size and orientation settings are not met (with the option to ignore the orientation)
• If the required number of pages is not met
• If there are blank pages in the document (with the option to consider pages empty if they only contain master page items, or if they contain only non printing items)
• If the bleed and slug setup settings are not met in the document (with the options to set maximum/minimum bleed and slug sizes)
Wow! Now that is a whole lot of checks that will make it so much safer and faster to lay out your documents. Anything else you think that should be included in Live Preflight?
The question that initiated this blog post was: "how can I change the default profile for all new documents?". Well, basically, all you need to do, is create and save your profile, then, in the Preflight Panel, choose Preflight Options from the fly out menu and choose your Working Profile; if you want this profile to be applied to all new documents, it is important that you make that change to the Preflight Options with no document open, so that this will become the default every time you create a new InDesign CS4 document.
Breathe in, relax, and once every so often, glance down to the bottom left of your application window and check the color of that circle... You'll be just fine.