To convert PDF Documents to Word format.

Convert.WordOutputOptions wordOutputOptions = new Convert.WordOutputOptions();

// Optionally convert only the first page
wordOutputOptions.SetPages(1, 1);

// Requires the Structured Output module
Convert.ToWord(filename, output_filename, wordOutputOptions);

To convert PDF Documents to Excel format.

Convert.ExcelOutputOptions excelOutputOptions = new Convert.ExcelOutputOptions();

// Optionally convert only the first page
excelOutputOptions.SetPages(1, 1);

// Requires the Structured Output module
Convert.ToExcel(filename, output_filename, excelOutputOptions);

To convert PDF Documents to PowerPoint format.

Convert.PowerPointOutputOptions powerPointOutputOptions = new Convert.PowerPointOutputOptions();

// Optionally convert only the first page
powerPointOutputOptions.SetPages(1, 1);

// Requires the Structured Output module
Convert.ToPowerPoint(filename, output_filename, powerPointOutputOptions);

Convert PDF to Office
Full sample code which shows how to convert generic PDF documents to Word, Excel, PowerPoint format