The .xls format was the default Microsoft Excel spreadsheet format from Excel 97 through Excel 2003. It uses the BIFF8 (Binary Interchange File Format version 8) within an OLE2 container — the same container as the .doc format. Despite .xlsx being the modern standard since 2007, .xls files remain common in accounting systems, ERP software, and older enterprise tools that have not been updated.
What is preserved when converting XLS to PDF
LibreOffice Calc opens .xls files and exports them to PDF with the following preserved: cell values, formula results (displayed as their calculated value, not the formula text), column widths and row heights, cell borders and background colours, basic number formatting (currency, percentages, dates), and sheet structure. Each sheet in the workbook becomes a section of the PDF.
Pivot tables are exported as their currently-displayed data — the pivot functionality does not transfer to PDF, but the visible data does. Simple charts (bar, line, pie) are exported as static images. Complex Excel-specific chart types may render differently in LibreOffice.
Using Filum's XLS to PDF tool
Filum's XLS to PDF tool sends the file to a LibreOffice Calc server. The file is uploaded over an encrypted connection, converted, and immediately deleted. No account is required. Conversion typically takes 5–20 seconds depending on the number of sheets and the complexity of formatting.
If columns are cut off at the right margin in the output PDF, the spreadsheet's print area settings are being applied. In LibreOffice Calc, the print area for each sheet is set separately. If you have access to the original file, setting a wider print area or scaling to fit one page wide before conversion produces better output.
.xls vs .xlsx
.xls is the BIFF8 binary format. .xlsx is the Office Open XML format, standardised as part of ECMA-376. Most modern Excel files are .xlsx. LibreOffice handles both, but .xlsx generally converts with higher accuracy because it is an open XML specification. If you can save the file as .xlsx from the source application, the Excel to PDF tool will give better results.