Combine multiple PDFs into one

Drop every PDF you want to combine into the workspace — two files or twenty. The file list shows each document with its page count, so you can confirm order before anything is produced. Drag files into the sequence they should appear in the final document: cover first, then body, then appendices.

Press merge and the files are concatenated in browser memory using a client-side PDF library. Pages keep their original content exactly — text stays selectable and vector-crisp, images keep their resolution, and embedded fonts travel with their pages. Preview the result, then download the single combined file. Nothing is uploaded at any point, which makes this suitable for contracts, financial records, and medical documents that cannot leave your device.

Ordering mistakes are the most common merge problem, and they are invisible until someone reads the document. Check three things before merging: the logical sequence of files (not the order they arrived by email), the page counts (the merged total should equal the exact sum of the parts), and the orientation of each page (fix rotated pages with the rotate tool before merging — it is much harder to spot afterwards).

If the same files will be combined repeatedly — monthly invoices, weekly reports, recurring chapter exports — note the working order somewhere reusable. The merge itself takes seconds; reconstructing which of eight similarly named PDFs came first is what actually costs time.

If the combined file will exceed email attachment limits (typically 20–25 MB), merge and then compress, or send the files separately — a bounced message wastes more time than the tidiness of one file is worth. If different recipients should see different parts, keep the documents separate rather than distributing one file with sensitive pages someone should not have.

Documents still in active review are also better left unmerged: separate drafts are easy to swap, while a merged file has to be un-merged to replace a single page. Treat merging as the final step of a document workflow, not an organizing one.

Merging is concatenation, not re-rendering: each source file's pages are copied into a new document as-is, so text remains selectable vector type, images keep their original resolution, and embedded fonts travel with the pages they belong to. Bookmarks and page structure from each source survive the trip as well — the combined file opens with the same internal navigation the parts had, which is why a merged report still jumps to its chapters.

What does not automatically carry over is document-level metadata and form consistency. The merged file typically inherits the title and author fields of whichever source went in first, so rename it afterward; interactive form fields from multiple sources can collide when the same field names appear twice (fill one, and its twin elsewhere updates too — test-fill before distributing); and applied digital signatures are invalidated by any change to the file, so sign after merging, never before.

Real merge jobs are rarely four clean exports from the same app. Scanned pages arrive as large image-heavy files with their own orientation quirks; print-to-PDF outputs may be a different page size (A4 mixed with Letter) than the office document they pair with; and every source can carry different metadata and compression. PDF handles mixed page sizes natively — each page keeps its own dimensions — so the combination is valid even when the sheets differ; readers and printers display each page at its own size.

Two preparations save rework. Fix rotation first: a sideways scan merged into a correct document is harder to notice afterwards than before, because attention drops once pages appear to belong together. And watch the total size: scans dominate it, since each page is a full-resolution image — if the merged result approaches email attachment limits (20–25 MB), compress the scan-heavy pages or split the document rather than fighting the bounce.