Your spreadsheet has 12 columns. Default portrait orientation in the PDF means columns 9-12 end up on page 2. Landscape would fit them all on one page — but only if you set it before converting.
Page Layout controls everything
Excel's Page Layout tab is where orientation lives. Page Layout > Orientation > Landscape (or Portrait). The setting is per-sheet — different sheets can have different orientations in one workbook.
Flint's Excel to PDF honours whatever you set.
When to pick landscape
Wider than tall: if your data has more columns than rows fit on a page. Multi-column tables: the natural reading direction is horizontal. Charts that are wider than tall: which is most of them.
For most analytical spreadsheets, landscape is the better default.
When to pick portrait
Few columns, many rows: classic list-of-data style. Single-column reports: narrative summaries with one or two side columns. Documents matching letter-style formatting: invoices, receipts, anything that should look like a document rather than a table.
Default portrait is fine if your data fits.
Mixed orientation across sheets
If you have a workbook with both wide data sheets and narrow summary sheets, set each sheet's orientation appropriately. The PDF will switch orientation between sheets — Acrobat handles this gracefully; some lighter PDF viewers may not.
For maximum compatibility, keep the whole PDF in one orientation.
FAQ
Can I set orientation per page?
Per sheet, yes. Per page within a sheet, no — Excel doesn't support that natively.
Will landscape make text too small?
Only if you also force-fit to one page. Landscape alone uses standard text size on a wider page.
Does orientation affect the underlying data?
No — only the print/PDF layout. The xlsx data is unchanged.
What about A4 vs Letter size?
Set separately in Page Layout > Size. A4 in the UK, Letter in the US — pick whatever your recipient expects.
Orientation is one setting away. Convert your Excel to PDF in whichever fits.