The Create PDF button on Quote

I was asked about the ability to restrict the creation of a PDF for a given quote until a couple business rules had been met.  As I thought about the solution, a couple ideas came to mind:

1. Add a record type for the ok Quotes and assign that record type a new layout that includes the Create PDF button.  Remove the Create PDF from the other page layout.
2. Modify the behavior of the existing Create PDF button to check the status first.
3. Create a new VF page to replicate the Create PDF functionality.

Given the timing and other project considerations, I opted for #2, if it was feasible.  I knew that #1 would work but I was worried about introducing a record type and then having to roll it back when another quote-related project went live.

To start, I had to figure out if I could see the code that the out-of-box button was calling to render the PDF.  With chrome it was pretty easy to inspect the element and see the code the button was calling.

With a minor bit of additional javascript, the quote's status can be interrogated first and an informational alert raised, if certain business criteria are met:

/*********************************************************************
if('{!Quote.Status}'!= 'XYZ' ) 
{
// do some business logic...
var isOk = true;  
} if(isOk) 
{ 
var pdfOverlay = QuotePDFPreview.quotePDFObjs['quotePDFOverlay']; 

pdfOverlay.dialog.buttonContents = "<input value=\'Save to Quote\' class=\'btn\' name=\'save\' onclick=\"QuotePDFPreview.getQuotePDFObject(\'quotePDFOverlay\').savePDF(\'0\',\'0\');\" title=\'Save to Quote\' type=\'button\' ><input value='Save and Email Quote' class='btn' name='saveAndEmail' onclick=\"QuotePDFPreview.getQuotePDFObject(\'quotePDFOverlay\').savePDF(\'1\');\"; title='Save and Email Quote' type='button' ><input value=\'Cancel\' class=\'btn\' name=\'cancel\' onclick=\"QuotePDFPreview.getQuotePDFObject(\'quotePDFOverlay\').close();\" title=\'Cancel\' type=\'button\' >"; 

//change this to use the correct template for your business/environment!! 
pdfOverlay.summlid = 'XXXXXXXXXXXXX'; 

pdfOverlay.setSavable(true); 

//change this to use the quote id 
pdfOverlay.setContents('/quote/quoteTemplateDataViewer.apexp?id={!Quote.Id}','quote/quoteTemplateHeaderData.apexp?id={!Quote.Id}'); 

pdfOverlay.display(); 
} 
else 
{ 
//raise an alert to let the user know about some business rule
alert('The Quote requires XYZ before the PDF can be generated.'); 
}

*************************************************************/