Pentaho can output reports in a variety of formats:
PDF
Excel (XLS)
Word (DOC)
Web Page (HTML)
Comma Separated Value (CSV)
PDF is useful if you want to report to look and print exactly the way it was designed, i.e. leveraging the "pixel-perfect" benefit of Report Designer to best effect. It is an open standard. It can't be edited easily, but it is the best choice if you wish to distribute a report file and want to guarantee that it looks the same for everyone. PDF files can be read with software such as Adobe Reader.
Warning: The following formats are designed for editing but not display. Your reports might not look exactly how you designed them (e.g. they might not fit a report onto one page), but they may offer other benefits.
Excel (XLS format) gives you a Microsoft Excel spreadsheet file. It is a proprietary format. You can open and edit it in application like OpenOffice and manipulate it just like any other spreadsheet. Note that any changes you make to the file will not be reflected on the server. If you want to share your findings, or if you find yourself making the same manipulations over and over, it might be worthwhile to have it written as a real report on the server.
Word creates a Microsoft Word compatible DOC file. It is a proprietary format. You can open and edit it in application like OpenOffice. Generally, XLS is a better option for editing.
Web Page (HTML) gives the fastest result, as it loads in your Web browser just like any other HTML page. It is an open standard. If you just want to quickly view some results, this is the easiest option.
Comma Separated Value (CSV) delivers a formatted test file that you can open in many different applications. It is an open standard. You can edit it like a spreadsheet, but it is limited in the types of information it can store. On the plus side, it is a very simple format that can be read anywhere.
The general rule of thumb is to use openstandard formats wherever possible, especially if you wish to share the file with others or store it for a long time.
