Document tools handle the formats that office work runs on: Word files, spreadsheets, CSV and rich text. The set is small and focused. DOC to PDF turns a Word document into a PDF that looks the same on any device, and PDF to DOC goes the other way by extracting a PDF's text into an editable Word file.
For spreadsheets, Excel to CSV and CSV to Excel move data between a plain text format and a proper workbook. CSV is the safer choice when you are importing into another system, and Excel is better when a person needs to read and edit the data. If an old RTF file is giving you trouble, the RTF Converter extracts the plain text from it.
A few expectations help. These tools run in your browser, so your files are not uploaded. Conversions focus on content, not perfect layout: PDF to DOC extracts text rather than rebuilding the original design, and spreadsheet conversion uses the first sheet. For data formats like JSON and XML, see the Converter Tools category, and for building PDFs from images or HTML, see PDF Tools.