Salesforce PDF Viewer with custom PDF page

1. First create a apex class with following contents:

global with sharing class QuoteCustomPdfGenerator {
    private ApexPages.StandardController sc;
    public Quote q {get; private set;}
    public String id {get; private set;}

    public QuoteCustomPdfGenerator(ApexPages.StandardController controller) {
        this.sc = sc;
        this.id = ApexPages.currentPage().getParameters().get('Id');
        this.q = [SELECT Id,Name From Quote WHERE Id=:this.id];
    }
    
    public PageReference viewPdf() {
        return null;
    }

    webService static String createQuotePdf(String Id) {
        try {
            PageReference pageRef = new PageReference('/apex/QuoteCustomPdfView?Id='+Id);
            Blob content = pageRef.getContent();
            QuoteDocument doc = new QuoteDocument(Document = content, QuoteId = Id);
            insert doc;

            return 'SUCCESS';
        } 
        catch(exception ex) {
           System.debug('--- Error ----------'+ ex);
           return ex.getMessage();
        }
    }
}

2. Now create a visualforce page with following contents (Name of visualforce page="QuoteCustomPdfView"):

<apex:page standardController="Quote" extensions="QuoteCustomPdfGenerator" action="{!viewPdf}" renderAs="pdf">
    This is my custom pdf for the quote=[[{!q.Name}]]
</apex:page>

3. Create a local js file with following contents:

function SaveQuoteAsCustomPDF(quoteId) {
    try {
        var res = sforce.apex.execute("QuoteCustomPdfGenerator","createQuotePdf",{Id : quoteId});
        if(res=='SUCCESS') {
            window.location.reload();
        }
        else {
            alert('Error in attaching file ----'+ res);
        }
    }
    catch(er) {
        alert(er);
    }
}

4. Upload the js file in static resource section with name = "SaveQuoteAsCustomPDF".
5. After upload done click on view and copy the url from browser.
6. Now create a custom button under Quote section in setup with following configurations
6.1: "Display Type" = "Detail Page"
6.2: "Behavior" = "Execute JavaScript"
6.3: "Content Source" = "OnClick JavaScript"
6.4: Put the following contents in the box below:

{!REQUIRESCRIPT("/soap/ajax/24.0/connection.js")}
{!REQUIRESCRIPT("/soap/ajax/24.0/apex.js")}
{!REQUIRESCRIPT("/resource/1470022474000/SaveQuoteAsCustomPDF")} /* Location from step 5 */

var pdfOverlay = QuotePDFPreview.quotePDFObjs['quotePDFOverlay'];
pdfOverlay.dialog.buttonContents = '<input value=\"Save Quote As PDF\"  class=\"btn\" name=\"save\" onclick=\"SaveQuoteAsCustomPDF(\'{!Quote.Id}\');\" title=\"Save Quote As PDF\" type=\"button\" /><input value=\"Close\"  class=\"btn\" name=\"cancel\" onclick=\"QuotePDFPreview.getQuotePDFObject(\'quotePDFOverlay\').close();\" title=\"Close\" type=\"button\" />';

pdfOverlay.setSavable(true);
pdfOverlay.setPDFContents('/apex/QuoteCustomPdfView?Id={!Quote.Id}',null,null);
pdfOverlay.display();

7. Add the button in quote page layout.
8. View details of a quote & click the button you added on step 7.