// Send Invoice as PDF using email to the associated client...
    @AuraEnabled
    webservice static Response_Wrapper emailInvoicePDF(Id InvoiceId){
      Freshbook__Invoice__c inv = getInv(InvoiceId);
      Response_Wrapper response;
      if(inv==null){
         response = new Response_Wrapper(false,'Insufficient Access to Invoice Object.');return  response;  
      }
      PageReference pdf = Page.PdfOfInvoice;// Replace PdfOfInvoice with your Page which render as PDF.
      pdf.getParameters().put('id', InvoiceId);
     // Blob b = pdf.getContentAsPDF();
      Blob b;
      if (Test.IsRunningTest()){b=Blob.valueOf('UNIT.TEST');}else{b = pdf.getContentAsPDF();}
      // Create Attachment Object to attach with Email
      Messaging.EmailFileAttachment efa = new Messaging.EmailFileAttachment();
      efa.setFileName(inv.Name+'.pdf');
      efa.setBody(b);
      // Define the email
      Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage(); 
      // Sets the paramaters of the email
      email.setSubject('PDF of Invoice - '+inv.Name);
      email.setToAddresses( new List<String>{inv.Freshbook__Client__r.Email__c} );
      //email.setbccAddresses( new List<String>{'amit@astreait.com'} );
      email.sethtmlBody('Hi '+inv.Freshbook__Client__r.Name+',<br/><br/> '
                             +'Please find the attached Invoice.'
                             +'<br/><br/>'+'Thanks,'+'<br/>'
                             +UserInfo.getName()+'<br/>'
                             +UserInfo.getOrganizationName());
      email.setFileAttachments(new Messaging.EmailFileAttachment[] {efa});
      // Sends the email
      //Response_Wrapper response;
      try{
           Messaging.SendEmailResult [] result = Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email});
      }catch(System.Exception e){
          if(e.getMessage().contains('SINGLE_EMAIL_LIMIT_EXCEEDED')){
              response = new Response_Wrapper(false,'SINGLE_EMAIL_LIMIT_EXCEEDED.');
          }else{
              response = new Response_Wrapper(false,'Exception Executed :'+e.getMessage());
          }
          return response;
      }
      response = new Response_Wrapper(true,'Success!');return response;
    }