Post your code.

Controller:

public class ONEN_EXT_AcknowledgeGift {

Opportunity opp;

OpportunityContactRole[] conRoles;

Contact primaryContact; Id primaryId;

public Boolean taxDeductible { get {return taxDeductible;} set {taxDeductible = value;} }

public ONEN_EXT_AcknowledgeGift(ApexPages.StandardController controller) {

this.opp = (Opportunity)controller.getRecord();

opp = [select id, Name, Amount, StageName, Tax_Receipt_Id__c from Opportunity where id = :opp.id];

conRoles = [select ContactId From OpportunityContactRole WHERE Opportunity.Id = :opp.id AND IsPrimary = true limit 1];

if (conRoles.size()>0) {

primaryID = conRoles[0].ContactId;

}

primaryContact = [select FirstName, LastName, Primary_Street__c, Primary_City__c, Primary_State_Province__c, Primary_Postal_Code__c from Contact where Id = :primaryID];

if ( opp.Tax_Receipt_Id__c == null ) {

taxDeductible = false;

} else {

taxDeductible = true;

}

}

public List<SelectOption> getOptions() {

List<SelectOption> options = new List<SelectOption>();

options.add(new SelectOption('thanks_only','Send a thank you note only'));

if ( taxDeductible ) {

options.add(new SelectOption('thanks_plus_receipt','Send a thank you note with attached tax receipt'));

options.add(new SelectOption('receipt_only','Attach a PDF of the tax receipt to the opportunity (for download)'));

}

return options;

}

public String attachments { get {return attachments;} set {attachments = value;} }

public pageReference acknowledgeGift() {

//create the PDF and attach it to the Opp

PageReference pdf = Page.taxReceipt;

pdf.setRedirect(true);

Blob pdfContent = pdf.getContent();

if ( opportunity.Tax_Receipt_Id__c != null ) {

Attachment doc = new Attachment(

Body = pdfContent,

Name = primaryContact.FirstName + ' ' + primaryContact.LastName + ' Tax Receipt #:' + opp.Tax_Receipt_Id__c,

ContentType = 'application/pdf',

ParentId = opp.id

);

insert doc;

}

... 

 First VF Page:

<apex:page standardController="Opportunity" extensions="ONEN_EXT_AcknowledgeGift" >

<apex:sectionHeader title="Acknowledge Gift">

<description>

<apex:outputText value="Use this page to acknowledge a gift and issue a tax receipt via email or attach a PDF of the tax receipt to the opportunity record."/>

</description>

</apex:sectionHeader>

<apex:form >

<apex:pageBlock title="Choose format:" >

<apex:selectRadio value="{!attachments}" id="attachments" layout="pageDirection">

<apex:selectOptions value="{!options}"/>

</apex:selectRadio>

<apex:outputtext rendered="{!!taxDeductible}">

<p><strong>There is not an option to send a tax receipt for this opportunity because this opportunity is not listed as Tax Deductible. If this is incorrect, return to the <a href="/{!opportunity.id}">{!opportunity.name}</a> record and mark the Tax Deductible checkbox to assign a Tax Receipt Id.</strong></p>

</apex:outputtext>

<apex:pageBlockButtons >

<apex:commandButton action="{!acknowledgeGift}" value="Send/Process"/>

</apex:pageBlockButtons>

</apex:pageBlock>

</apex:form>

</apex:page>

Second VF Page, called from the first:

<apex:page standardcontroller="Opportunity" extensions="ONEN_EXT_AcknowledgeGift" renderAs="PDF">

<apex:panelGrid columns="2" id="theGrid">

<apex:outputText value="Name: " styleClass="labelCol"/>

<apex:outputText value="{!Opportunity.Name}" styleClass="dataCol" />

<apex:outputText value="Amount: " styleClass="labelCol" />

<apex:outputText value="{!Opportunity.Amount}" styleClass="dataCol" />

<apex:outputText value="Stage: " styleClass="labelCol" />

<apex:outputText value="{!Opportunity.StageName}" styleClass="dataCol" />

</apex:panelGrid>

</apex:page>