How to Merge PDF Files Online — 4 Free Methods

PDFJolt merges multiple PDF files into a single document directly in your browser — drag, drop, rearrange, and download. Your files never leave your device because all processing happens client-side using WebAssembly, making it the fastest and most private way to combine PDFs online.

Why Merging PDFs Is a Common Need

Combining PDF files is one of the most frequent document tasks people face. You might need to merge a cover letter with a resume, combine multiple invoices into a single file for accounting, join scanned pages into one document, or assemble a report from separate chapter files. Despite how common this task is, neither Windows nor macOS includes a built-in PDF merging tool that is obvious and easy to find.

The result is that millions of people search for "merge PDF" every month — and most end up uploading their documents to online tools that process files on remote servers. For non-sensitive documents, this may be acceptable. For contracts, financial records, or personal documents, server-side processing introduces unnecessary privacy risk.

Method 1: PDFJolt (Browser-Based, Private, Free)

PDFJolt's PDF merger combines your files entirely in the browser using WebAssembly. No file uploads, no accounts, no cost.

Step-by-Step Instructions

1. Open pdfjolt.ca/tools/pdf/merge-pdf in any modern browser.
2. Drag and drop all the PDF files you want to combine into the upload zone. You can also click to browse and select multiple files at once.
3. PDFJolt displays thumbnail previews of each file. Drag the thumbnails to rearrange the order. The first file in the list becomes the first pages of the merged document.
4. Click Merge. Processing happens instantly in your browser.
5. Download the combined PDF.

The entire process takes under 30 seconds for most documents. Since there is no upload step, even large files merge quickly — the only bottleneck is your browser's processing speed, not your internet connection.

Why PDFJolt Is the Best Option

• Privacy — Your files never leave your device. Period.
• Speed — No upload/download time. Merging happens in milliseconds for typical documents.
• No account required — Use the tool immediately without signing up.
• Lossless operation — Pages are combined without recompression. Image quality, fonts, and formatting are preserved exactly.
• Works on mobile — Full functionality in mobile browsers on iOS and Android.

Method 2: Adobe Acrobat (Paid)

Adobe Acrobat Pro ($19.99/month) includes a Combine Files feature. Open Acrobat, go to Tools > Combine Files, add your PDFs, arrange the order, and click Combine. Adobe also offers a free online merger at adobe.com/acrobat/online/merge-pdf, but it requires an Adobe account and uploads your files to Adobe's servers.

The desktop version processes files locally, which is good for privacy. But at $240 per year, it is an expensive solution for an occasional task. If you merge PDFs frequently as part of a professional workflow and already pay for Creative Cloud, Acrobat is a reasonable option. For everyone else, it is overkill.

Method 3: macOS Preview

On a Mac, you can merge PDFs using Preview, though the process is not intuitive. Open the first PDF in Preview, go to View > Thumbnails to show the sidebar, then drag additional PDF files into the thumbnail sidebar at the position where you want them inserted. Finally, save the combined document via File > Export as PDF.

This method works but has notable limitations:

• It is easy to accidentally insert pages in the wrong position.
• There is no visual merge queue — you are editing the first document in place.
• macOS only — not available on Windows, Linux, or mobile devices.
• Merging more than 3-4 files becomes cumbersome because you must drag each one individually.

Method 4: Command Line (Technical Users)

On Linux and macOS, you can merge PDFs using command-line tools. The most common options are pdftk and Ghostscript:

pdftk file1.pdf file2.pdf file3.pdf cat output merged.pdf

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=merged.pdf file1.pdf file2.pdf

The pdftk approach produces a lossless merge similar to PDFJolt. The Ghostscript method re-renders the PDF, which can slightly alter formatting but also reduces file size. Command-line tools are powerful and private (everything stays local), but they require installation, terminal familiarity, and offer no visual preview of the result.

Comparison: PDF Merging Methods

Feature	PDFJolt	Adobe Acrobat	macOS Preview	Command Line
Price	Free	$19.99/mo	Free (Mac only)	Free
Privacy	Files never uploaded	Local (desktop)	Local	Local
Drag-and-drop	Yes	Yes	Partial	No
Visual reordering	Yes	Yes	No	No
Works on mobile	Yes	App required	No	No
Account required	No	Yes	No	No
Lossless merge	Yes	Yes	Yes	Depends
Cross-platform	Yes	Yes	No	Linux/Mac

Tips for Merging PDFs

• Check page orientation before merging. If some documents are portrait and others landscape, the merged PDF will reflect those differences. Rotate pages before merging if you want a consistent orientation.
• Name your files in order. If you are merging chapters or numbered documents, name them 01-intro.pdf, 02-chapter1.pdf, etc. This makes it easy to verify the correct order in PDFJolt's preview.
• Compress after merging if needed. Merging does not change file sizes — the merged PDF is roughly the sum of the original sizes. If the result is too large for your needs, run it through PDFJolt's PDF compressor afterward.
• Split first if you only need certain pages. If you need pages 3-5 from one PDF and pages 1-2 from another, use PDFJolt's Split PDF tool to extract the pages you need, then merge the results.

Common Use Cases

Job Applications

Many job applications require a single PDF containing your resume, cover letter, and references. Upload all three documents to PDFJolt, arrange them in order (cover letter first, resume second, references third), and merge. The result is a polished, single-file application package.

Invoice Bundles

Accountants and freelancers often need to combine monthly invoices into quarterly or annual bundles for record-keeping or tax filing. PDFJolt handles dozens of invoice PDFs at once — drag them all in, verify the chronological order, and merge into a single document.

Scanned Document Assembly

If you have scanned individual pages as separate PDFs (common with flatbed scanners), merging them into a single multi-page document is essential for readability and organization. After merging, you can run the combined file through PDFJolt's compressor to reduce the total size.

Academic Papers and Reports

Research papers, thesis chapters, and business reports are often written in sections by different authors. Merging the final sections into one document with consistent page flow is a standard step in the publication process.

What Happens Inside a PDF Merge

Understanding the technical process helps explain why merging is lossless. A PDF file is internally structured as a series of objects — page objects, font objects, image objects, and a cross-reference table that links them together. When PDFJolt merges two PDFs, it copies all objects from both files into a new PDF and builds a new cross-reference table that includes every page from both documents. No images are recompressed, no fonts are re-embedded, and no text is re-rendered. The operation is purely structural.

This is fundamentally different from "printing to PDF" or screenshot-based approaches, which re-render each page as a flat image and lose text selectability, bookmarks, hyperlinks, and form fields.

Privacy When Merging Documents

The documents people merge are often sensitive: legal contracts with exhibits, financial statements with supporting schedules, medical records with lab results. According to a 2025 survey by the International Association of Privacy Professionals, 42% of data breaches in professional services involved documents shared through or processed by third-party cloud tools.

PDFJolt's browser-based processing eliminates this attack surface. Your files are loaded into browser memory, merged using WebAssembly-compiled code, and the result is saved directly to your device. No network requests carry your document data. You can confirm this by monitoring your browser's network tab during the merge — zero file uploads occur.

For sensitive document workflows, client-side processing is not a luxury feature. It is a baseline security requirement that every tool should meet but few actually do.