DOC, PDF, XLS, PPT, Ebook Search Engine with Instant Preview and Download Link
It is not impossible to search all these kind of file types using Google search engine, but you will find it easier if you use DocJax search engine instead. By utilizing Scribd iPaper technology, DocJax enables you to preview the document to find out if it is worth downloading. Moreover, it would be much easier to type simply the keyword and get all the file types (doc, pdf, xls, ppt) instead of using the complex filetype search operator of Google to get them all in one search.
Here is some of the results when I look for photoshop ebook:

While you can get all the file types in one go, you can also narrow the result to any of these file formats by clicking the filetype link.

Additionally, the search result can also be filtered using most search operators such as site:. So, if you are looking for downloadable documents available only in adobe.com, you can type, for example, “photoshop site:adobe.com”.
Visit DocJax to search PDF, DOC, PPT, XLS online
February 26th, 2010 at 7:32 am
[...] or Yahoo. Third, use a dedicated search engine that provides documents in one specific file format. DocJax is a ppt search engine that had been posted here a few months ago. It works great, but if you need [...]