Hi Guys,

It seems to be a complicated issue and many of us have different results...

Why is it that this code works well:
<apex:page standardController="Account" recordSetVar="account" renderas="pdf">
   <apex:form >
    <apex:pageBlock >             
        <apex:pageBlockTable value="{!account}" var="a">
            <apex:column value="{!a.Id}" />
            <apex:column value="{!a.Name}" />     
        </apex:pageBlockTable>             
    </apex:pageBlock>
   </apex:form>
</apex:page>

But this one is not?

<apex:page standardController="Invoice__c" recordSetVar="invoice" renderas="pdf">
   <apex:form >
    <apex:pageBlock >             
        <apex:pageBlockTable value="{!invoice}" var="a">
            <apex:column value="{!a.Id}" />
            <apex:column value="{!a.Name}" />     
        </apex:pageBlockTable>             
    </apex:pageBlock>
   </apex:form>
</apex:page>

My Apex Class is:
global class attachPDFToInvoice {
    
    private final Invoice__c i; //Invoice object
    
    //constructor
    public attachPDFToInvoice(ApexPages.StandardController standardPageController) {
        i = (Invoice__c)standardPageController.getRecord();
    }
    
    //method called from the Visualforce's action attribute
    public PageReference attachPDF() {
        
        //generate and attach the PDF document
        PageReference pdfPage = Page.PDF_Invoice;
        Blob pdfBlob; //create a blob for the PDF content
        if (!Test.isRunningTest()) { //if we are not in testing context
            pdfBlob = pdfPage.getContent(); //generate the pdf blob
        } else { //otherwise, we are in testing context and getContent() gets funky so create the blob manually
            pdfBlob = Blob.valueOf('Some Text for a boring PDF file...');
        }
        Attachment attach = new Attachment(parentId = i.Id, Name = 'Invoice.pdf', body = pdfBlob); //create the attachment object
        insert attach; //insert the attachment
        
        
        //redirect the user
        PageReference pageWhereWeWantToGo = new ApexPages.StandardController(i).view(); //we want to redirect the User back to the Invoice detail page
        pageWhereWeWantToGo.setRedirect(true); //indicate that the redirect should be performed on the client side
        return pageWhereWeWantToGo; //send the User on their way
    }

}
In all cases, the file is attached to my Invoice Custom Object but only the first example works with Account fields.

Thanks for your help!
Eric