Your contract is Letter, your spec sheet is A4, your diagram exported as A3. They all need to be one PDF. Should they stay their original sizes, or get squashed to a single uniform size?
It depends on what happens next. Flint gives you both options.
Keep originals: best for digital reading
If the merged file will be read on screen, keep each page its original size. Readers scale to fit the viewport anyway, so A4 vs Letter doesn't matter visually. Drag your files into merge PDF and merge — Flint preserves every page's dimensions by default. Your A3 diagram remains a full-size A3 when zoomed in.
Normalise to one size: best for printing
If you'll print the merged file, mixed sizes can confuse the printer. Pick one target size — usually A4 or Letter, whichever your office uses — and have every page scaled to fit. Use edit PDF after merging to resize all pages to A4 with margins, or pre-convert each source to your target size before merging.
The cropping trade-off
Normalising means either scaling or cropping. Scaling preserves all content but shrinks larger pages (A3 spec sheets become harder to read). Cropping keeps the resolution but cuts the edges off oversized pages. For mixed packs, scaling is usually safer. The exception: when oversized pages are mostly whitespace and cropping costs nothing.
Sizes that recipients can't print
If your recipient is in the US and you send A4, they can still print on Letter — printers auto-scale slightly. The other direction works too. Real problems start at A3+: not every home printer handles those, and the recipient might receive a mysteriously cropped page. Mention oversized pages in your covering email.
FAQ
Will the merged file's metadata show one size or many?
PDFs don't have a single document size — each page has its own. The merged file accurately reports each page's dimensions.
Can I keep most pages original but resize one?
Yes, edit PDF lets you resize specific pages.
What if my source files are weird sizes (postcard, label)?
Flint preserves whatever the source size is. Tiny pages stay tiny. Resize during edit if needed.
Does this affect file size?
Page dimensions barely affect file size. Content (text, images) is what determines it.
Keep them mixed or normalise them — your call. Merge different-sized PDFs.