How to Merge PDF Files Into One Document (Free, 2026)

Adobe Acrobat provides the most control over PDF merging:

• 1. Open Adobe Acrobat.
• 2. Go to Tools → Combine Files.
• 3. Click Add Files and select your PDFs.
• 4. Drag to reorder, then click Combine.

Acrobat lets you add bookmarks, rearrange individual pages, and combine different file types (Word, Excel, images) into a single PDF. However, it requires a paid subscription ($19.99/month).

For developers or power users, you can merge PDFs from the command line:

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=merged.pdf file1.pdf file2.pdf file3.pdf

pdfunite file1.pdf file2.pdf file3.pdf merged.pdf

from PyPDF2 import PdfMerger
merger = PdfMerger()
for pdf in ["file1.pdf", "file2.pdf", "file3.pdf"]:
    merger.append(pdf)
merger.write("merged.pdf")
merger.close()

These methods are great for automating PDF merging in scripts or workflows.

• Check page sizes — if your PDFs have different page sizes (Letter vs A4), the merged document will preserve each page's original size. This is usually fine but may look inconsistent when printed.
• Compress after merging — the merged file will be roughly the sum of all input files. Use our Compress PDF tool to reduce the final size.
• Check the page order — before sharing, scroll through the merged PDF to make sure pages are in the right order.
• Consider bookmarks — for long merged documents, adding bookmarks helps readers navigate. Adobe Acrobat and some online tools support this.

Reformat's free plan supports merging multiple PDFs up to a total of 10 MB. Pro users can merge files up to 100 MB total.

No. Merging simply combines the files — no recompression or quality loss occurs. The merged PDF preserves the exact same content and quality as the originals.

You'll need to unlock the PDFs first. Remove password protection from each file, merge them, then re-apply protection to the merged file if needed.

Yes! Reformat's online merger works in any mobile browser — iPhone, Android, or tablet. Just upload your files and download the merged PDF.

With our online tool, you can reorder the files before merging. For page-level rearrangement, use Preview on Mac or Adobe Acrobat.