When to turn a spreadsheet into a PDF
A spreadsheet is built for working with data; a PDF is built for reading it. When you send a price list, a statement, a timetable, or a summary table to someone who only needs to read it, a PDF avoids accidental edits, hides formulas, and opens the same way on every device without needing Excel.
How the conversion works
Excel to PDF reads the first sheet of your XLSX, XLS, or CSV file and draws it as a table on A4 pages: the first row is styled as a header, alternate rows are lightly shaded, and each cell gets a thin border. Values appear as they are displayed in your spreadsheet — formulas show their calculated results, and dates and numbers keep their formatting.
The conversion runs in your browser, so your spreadsheet is not uploaded.
Limits you should know about
Only the first sheet is converted. Column widths are scaled so the table fits the page width, which makes very wide spreadsheets small and hard to read, and cell text longer than 50 characters is cut off. Fonts, colors, charts, images, merged cells, and print settings from the original file are not reproduced, and characters the PDF font cannot display (for example non-Latin scripts) are replaced with a question mark.
For a pixel-exact PDF with charts, multiple sheets, and your own formatting, use File → Save as → PDF (or Export) in Excel.
Getting the best result
Put the sheet you want to convert first in the workbook, keep columns narrow, and make the first row a clear header. For wide tables, consider hiding unneeded columns before converting. A CSV file works well too — the first line is treated as the header row.