How can I send an email while using PageReference getContent() method in Salesforce?

Hello,

PageReference ref = Page.PDF_DEMO;
Blob b = ref.getContentAsPDF();

Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();

Messaging.EmailFileAttachment efa1 = new Messaging.EmailFileAttachment();
efa1.setFileName('attachment_WORK.pdf');
efa1.setBody(b);

String addresses;
email.setSubject( Subject +String.valueOf(DateTime.now()));
email.setToAddresses( EmailIds );
email.setPlainTextBody(Body);
email.setFileAttachments(new Messaging.EmailFileAttachment[] {efa1});
Messaging.SendEmailResult [] r = Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email});