How to merge PDF files
- Drop your files onto the drop zone above, or click it to pick them. You can select several PDFs at once and add JPG, PNG, WebP or HEIC images alongside them.
- Check the file list and use the up and down arrows next to each file to put them in the order you want; the first file in the list becomes the first pages of the merged PDF.
- Click Merge PDF. All pages of each PDF are copied in sequence, and each image is placed on its own page.
- Download the combined file and open it to confirm the page order.
The merge is done by pdf-lib running inside your browser tab, so your documents are never uploaded to a server. That makes the tool suitable for contracts, invoices, medical forms and other files you would rather not hand to a third-party service.
What happens when PDFs are merged
A PDF is not a single stream of text; it is a collection of numbered objects (pages, fonts, images, content streams) tied together by a cross-reference table. Merging creates a new, empty document and then copies the page objects from each source file into it, along with everything those pages depend on. Because the original page content is copied rather than redrawn, text stays selectable, vector graphics stay sharp and embedded images are not recompressed.
Images work differently. A JPG or PNG has no page of its own, so the tool creates a new page sized to the picture and draws it onto that page. JPG files are embedded unchanged. PNG, WebP and HEIC images (HEIC is the iPhone photo format) are first converted to high-quality JPEG in the browser, so any transparent areas become white. Images are not turned into text, so words in a photographed document will not be searchable.
| Input | How it is added |
|---|---|
| Every page copied unchanged, in its original order | |
| JPG | One new page per image, image data unchanged |
| PNG / WebP / HEIC | Converted to JPEG, then one page per image |
Tips and limitations
- Need only some pages? Merge first, then delete what you don't want with Remove PDF Pages, or pull out a range with Split PDF.
- Mixed orientations are preserved: a landscape page stays landscape. If a scanned page comes out sideways, fix it afterwards with Rotate PDF.
- Password-protected or encrypted PDFs are not supported. Unlock it first with Unlock PDF (you need its password), then come back.
- Interactive features such as bookmarks (the outline panel) and some form fields may not carry over, because they belong to the source document rather than to individual pages.
- Very large merges are limited by your device's memory rather than by an upload cap. If the browser struggles, merge in smaller batches and then merge the results.
Frequently asked questions
Is there a limit on how many PDFs I can merge?
There is no fixed file count or size limit. The practical limit is the memory available to your browser, since all the work happens on your device.
Will merging reduce the quality of my PDFs?
No. Pages are copied as they are, so text, fonts and images keep their original quality. The merged file is usually close to the combined size of the inputs.
Can I combine photos and PDFs in one file?
Yes. Add JPG, PNG, WebP or HEIC images to the same list as your PDFs and move them into position with the arrows. Each image becomes a single page. For a PDF made only of photos, with A4 or Letter page sizes and margins, use JPG to PDF.
Why does my file fail to load?
The most common cause is encryption: password-protected PDFs cannot be opened by the tool. A damaged or incomplete download can also fail; try opening it in a PDF viewer first.