Got some problem with my Mac last night, not a problem actually. After uncompressed some zip file into pdf, my MacBook fan keep running so fast, and when I look at Activity Monitor, ATSServer process use my CPU so much. At first, I didn’t realized it got something to do with the pdf file, but then after I look for an answer, I found that it was the problem.

I found the solution here. It says that, if I have new pdf (and other kind of files), Spotlight will make a database of the file content, so it will a database of all text in that document (for pdf, doc, etc). Later if I want to search some text on my document, I will find it faster.

The solution is: Open up System Preferences -> Spotlight Preferences -> Click Privacy button -> Click + button at bottom left and add the directory where you’ve just put your PDF files.

But, if I applied this, the document content is not at database, can’t find its content easily using Spotlight. In my case, I let ATSServer work for a while. I know it won’t be long and it didn’t make any damage to my Mac.