Render and combine PDF files into one

Render PDF files from HTML templates in Rails can be done using WickedPDF.

First you need to use ActionView to render HTML to a string:

def render_to_string(data)
  action_view = ActionView::Base.new
  action_view.view_paths = ActionController::Base.view_paths

  action_view.class_eval do
    include ApplicationHelper
    include PDFHelper
    # or other helpers
  end

  action_view.render template: 'pdf/template.html',
                     layout: 'layout/pdf.html',
                     locals: { data: data }
end

Then you can render pdf with the desired settings like this:

# first pdf file with some view settings and values from data1...
pdf1 = WickedPdf.new.pdf_from_string(
        render_to_string(data1), {
            pdf: 'report1',
            page_size: 'Letter',
            orientation: 'Portrait'
        })
# ...and second pdf file with some view settings and values from data2
pdf2 = WickedPdf.new.pdf_from_string(
        render_to_string(data2), {
            pdf: 'report2',
            page_size: 'Letter',
            orientation: 'Landscape'
        })

And now you can combine it with CombinePDF gem, that provide you parse method to get PDF content and to_pdfmethod to render the result back to PDF.

combiner = CombinePDF.new
combiner << CombinePDF.parse(pdf1)
combiner << CombinePDF.parse(pdf2)
combiner.to_pdf