Generating and sending PDF in ActionMailer with WickedPDF - ruby-on-rails

Question

i am using rails 4.2 and am generating pdfs in actionmailer with following code:
attachments["abc.pdf"] = WickedPdf.new.pdf_from_string(
render_to_string(template: "pdf_templates/abc.html", header: {
content: render_to_string(layout: "header.html")
}, margin: {
top: 50, left: 50
})
)
mail to: #user.email, subject: "bla blubb"
Its working fine and rendering the abc.html.erb. but it ignores margin-tags and the header file... if i put an error into header.html.erb rails is shouting - so it must be found and processed.
i also tried this but same issue:
pdf = render template: "pdf_templates/abc.html", footer: {spacing: 20, left: "ABDCDSAFASDF"}
attachments["abc.pdf"] = WickedPdf.new.pdf_from_string(pdf)
i read about some problems with ActionMailer but cant solve them, cause i am using rails 4:
wicked_pdf not loading header or footer in ActionMailer
Rails3 - wicked_pdf gem, footer issue when calling from action mailer model

Answer 1

Funny, thought that i tried the include which unixMonkey recommend. Now I tried again and it works with following code... Thank you for pushing me into the right direction.
class WelcomeMailer < ApplicationMailer
include PdfHelper
helper(MailerHelper)
def new_customer(user)
#user = user
test = render_to_string_with_wicked_pdf(
pdf: "test.pdf",
template: "pdf_templates/abc.html",
header: {html: {template: "pdf_templates/header.html"}}
)
attachments["abc.pdf"] = test
mail to: #user.email, subject: "blaa blubb"
end
end