Hexo tag for embeded pdf
$ npm install --save hexo-pdf
{% pdf http://7xov2f.com1.z0.glb.clouddn.com/bash_freshman.pdf %}
{% pdf https://drive.google.com/file/d/0B6qSwdwPxPRdTEliX0dhQ2JfUEU/preview %}
{% pdf http://www.slideshare.net/slideshow/embed_code/key/8Jl0hUt2OKUOOE %}