You have a cover letter, a CV, three scanned certificates, and a reference — six files that need to arrive as one document, in the right order, before a deadline. Merging PDFs is a mechanical task, and the good news is that you almost certainly already have a tool that does it.
Check what you already have first
Before visiting any website, check your own machine. For a great many people this is the whole answer.
macOS. Preview merges PDFs natively and most Mac users do not know it. Open the first PDF, choose View → Thumbnails to show the sidebar, then drag the other PDF files into that sidebar at the position you want them. Drag thumbnails to reorder. Then File → Export as PDF. Note that plain "Save" sometimes only edits the original, so use Export to produce the combined file.
Windows. There is no built-in merge, but there are two easy routes. Free desktop applications such as PDF24 Creator and PDFsam Basic do it offline in a few clicks. Or, if the files are short, print each to PDF into a single job — clumsier, but it needs nothing installed.
Linux. If you have Poppler installed, it is one command: pdfunite file1.pdf file2.pdf file3.pdf out.pdf. Ghostscript and qpdf --empty --pages *.pdf -- out.pdf do the same job.
Any platform, using tools you have. LibreOffice Draw opens PDFs and can assemble them. And if the documents are already in Word or Google Docs, combining them there and exporting once produces a cleaner result than merging the exports.
Doing it locally means nothing gets uploaded, there are no daily limits, and it works offline. For anything containing personal or client information, this is the route to prefer.
Merging online
If you would rather not install anything, plenty of free web tools merge PDFs: iLovePDF, Smallpdf, Sejda, PDF24, and others. The process is the same everywhere.
- Upload your files, usually all at once by dragging them in.
- Set the order. You will see thumbnails; drag them into sequence. This is the step people rush and regret — check it before proceeding.
- Merge, and wait for processing.
- Download the combined file.
- Open it and page through. Confirm the order, that no file was silently dropped, and that page orientation is consistent.
Be aware of what you are accepting. These tools are server-side: your documents are uploaded to somebody else's infrastructure, processed there, and deleted according to their stated retention policy. For a set of holiday photos this is unremarkable. For scanned passports, financial statements, or client files, it is worth pausing over — the local methods above avoid the question entirely. Are online PDF editors safe? goes into the trade in more detail.
Free tiers also carry caps: a few documents per day, or per-hour task limits, or a maximum file size. Hitting one mid-deadline is a familiar frustration.
To be direct about our own scope: Docento.app is an editor rather than a merge tool. It signs, annotates, and fills existing documents locally, and it compresses them. For merging, use one of the options above — we would rather point you somewhere that does the job than pretend we do.
Getting a good result
Order the files before you start. Rename them 01-cover.pdf, 02-cv.pdf, 03-certificates.pdf. Most tools respect filename order on upload, which turns the reordering step from fiddly dragging into nothing.
Watch for mixed page sizes. Merging an A4 report with US Letter scans produces a document that shifts size as you page through it, and prints inconsistently. If it matters, normalise the pages first.
Watch for mixed orientation. Scans often arrive rotated. Fix rotation before merging, not after — see how to rotate a PDF page.
Expect the size to add up, and then some. Merging five 2 MB scans gives you a 10 MB file that many mail servers will bounce. Compress the merged file before sending; scanned pages usually shrink dramatically with no visible loss.
Check that bookmarks and links survived. Merging often discards outline bookmarks and can break internal links. If you are combining reports with navigation, verify it in the output.
Do not merge a signed document you need to stay verifiable. If a PDF carries a certificate-based digital signature, merging it into another file invalidates that signature — the signature covers the file, and the file has changed.
After merging
The combined document usually needs finishing touches, and that is where an editor earns its place. You can add your signature to the assembled report, add page numbers or a date with the text tool, highlight the sections a reviewer should read first, or add a "DRAFT" mark before circulating it.
If you need the opposite operation later, extracting pages from a PDF covers splitting a combined file back apart.
