add PDF vignette to CRAN
diff --git a/docs/awesome_table_in_pdf.Rmd b/docs/awesome_table_in_pdf.Rmd
index c66b31c..49724f7 100644
--- a/docs/awesome_table_in_pdf.Rmd
+++ b/docs/awesome_table_in_pdf.Rmd
@@ -6,9 +6,21 @@
   pdf_document:
     toc: true
     toc_depth: 2
+header-includes:
+  - \usepackage{booktabs}
+  - \usepackage{longtable}
+  - \usepackage{array}
+  - \usepackage{multirow}
+  - \usepackage[table]{xcolor}
+  - \usepackage{wrapfig}
+vignette: >
+  %\VignetteIndexEntry{Create Awesome PDF Table with knitr::kable and kableExtra}
+  %\VignetteEngine{knitr::rmarkdown}
+  %\VignetteEncoding{UTF-8}
 ---
 
 > Please see the package [documentation site](http://haozhu233.github.io/kableExtra) for how to use this package in HTML and more. 
+
 # Overview
 The goal of `kableExtra` is to help you build common complex tables and manipulate table styles. It imports the pipe `%>%` symbol from `magrittr` and verbalize all the functions, so basically you can add "layers" to a kable output in a way that is similar with `ggplot2` and `plotly`.