You might have searched a lot for a particular pdf or a doc file on Google. Even if you try searching 'so and so content pdf', you may not see the results with pdf. If you are specifically in need of pdf file, then how do you search for it?
Yes, you can get the results only as pdf's. For this, you can simply search as 'pdf:the content that you want to search'. This is a simple geeky way to search a specific file of your interest. I have pasted a screenshot of an example below.
