Gộp PDF
Gộp nhiều file PDF thành một bản duy nhất, kéo thả để đổi thứ tự, chọn khổ giấy, lề và chèn trang trắng phân cách giữa các file.
1. Select PDF Files
Drag and drop your PDF files here
or click to browse
Supported formats: PDF
Max 100 MB per file · 400 MB total per batch · unlimited file count.
2. Merge Settings
Advanced options
Preview
Add PDF files to preview the merge order here
Each tile shows the cover of one source file. Drag the file list to change order.
Tip: drag and drop files in the list above to reorder them. Files merge in the order shown.
Merge PDF combines multiple PDF files into a single document directly inside your browser. It uses pdf-lib for assembly and PDF.js for thumbnail rendering, so your files never leave your device. The output preserves selectable text, embedded fonts, and image quality from the source files.
What it does
Drop in two or more PDFs, drag to set the merge order, and produce one combined file. You can keep each source file's original page size or normalise everything to a chosen standard (A4, Letter, and so on), add margins, force a single orientation, and optionally insert a blank divider page between files.
Who it is for
- Office staff bundling reports, invoices, and signed contracts into one deliverable.
- Students compiling assignments, references, and lecture notes into a single submission.
- Designers and printers consolidating chapter PDFs before imposition.
- Lawyers, accountants, and HR teams combining scans and exports for archiving.
When and where to use it
Use it whenever you need a single PDF instead of a folder of files: emailing one file is easier than attaching many, archives prefer a single document per case, and printers prefer a sequential file. The tool runs at /merge-pdf in any modern browser. Total batch size up to 400 MB; per-file cap 100 MB.
Why use a browser-side merger
Cloud mergers upload your documents and may rasterise them, breaking text selection. This tool processes files locally, copies pages with pdf-lib (no rasterisation when keeping the original size), and never sends content to a server.
How to merge PDF files
- Drop your PDFs into the dropzone, click Upload PDF files, or fetch one from a URL.
- Drag rows in the file list to set the order. Use the X icon to remove any file.
- Pick merge settings: keep the original page size or normalise, force orientation, choose margins, and decide whether to insert blank divider pages.
- (Optional) Open Advanced options to set the output filename, document title, and author metadata.
- Toggle the checkboxes in the preview to include or exclude any file in the final merge.
- Click Preview PDF for a slide-over preview, then Download Merged PDF to save the combined file.
Every control, explained
1. Select PDF Files
- Upload PDF files: opens a file picker; select one or many PDFs at once.
- From URL: pastes a PDF URL and adds the remote file to the batch when CORS is allowed.
- Drag and drop dropzone: drag PDF files from your OS file manager to add them.
- Added files list: each row shows position number, filename, page count, size, drag handle, and a remove button.
- Clear all: removes every file and starts over.
2. Merge Settings
- Page size: keep each file's native size, or normalise to A4, A3, A5, US Letter, or US Legal.
- Page orientation: keep original, or force every page to portrait or landscape.
- Margins: optional whitespace around each page (none, small 18 pt, medium 36 pt, or large 54 pt). Margins only apply when normalising page size or orientation.
- Add blank page between files: inserts a separator page after every source file (useful for double-sided printing).
- Output filename: base name for the saved PDF (the .pdf extension is added automatically).
- Document title / Author: written into PDF metadata; viewers display them in the document info panel.
3. Preview
- Select all / Deselect all: toggle every source file's inclusion in the merge.
- Grid view: thumbnail of the first page of each file plus filename and page count.
- List view: compact rows with checkbox, mini thumbnail, name, and size.
- Tile checkbox: toggle whether that file is part of the merge.
- Preview PDF: opens a slide-over with the merged result rendered live.
- Download Merged PDF: saves the merged file with your chosen output filename.
Practical tips
- Keep Page size and Orientation on Keep original when you want a fast, exact merge with no re-layout.
- Normalise to A4 or US Letter only when the source files have inconsistent sizes and you need a uniform document for printing or archiving.
- Set Add blank page between files to Yes for duplex printing so each new section starts on a right-hand page.
- For very large batches, prefer a desktop browser to avoid mobile memory limits.
Is this Merge PDF tool free and private?
Yes. The merge runs locally with pdf-lib and the Canvas API for thumbnails. Files are never uploaded to a server, there are no watermarks, and no account is required.
How many files can I merge at once?
The current limit is 100 MB per file and 400 MB per batch. The number of files is unlimited, but very large batches can be heavy on memory, especially on mobile browsers.
Will text and links remain selectable?
Yes when Page size and Orientation are Keep original: pdf-lib copies pages directly. When normalising, pages are embedded as XObjects, which still keeps text selectable, but vector annotations may be flattened.
Can I reorder files after adding them?
Yes. Drag the rows in the file list to change the merge order, or drag tiles in the preview list. The output respects the order shown.
Can I exclude specific files without removing them?
Yes. In the preview section, uncheck the tile to skip that file in the merged output. Re-check it later to include it again.
What happens with password-protected PDFs?
Encrypted PDFs cannot be merged until they are unlocked. Remove the password in another viewer and re-add the file.