맥(Mac)에서 PDF 병합하는 방법 (무료 포함 3가지 방법)

Mac users have it better than Windows users when it comes to PDF handling. Preview — the app that ships with every Mac — can merge PDFs without installing anything. But Preview's merge feature is hidden behind a non-obvious interface, and it has some quirks that trip people up.

Here are three ways to merge PDFs on Mac, from simplest to most powerful.

Method 1: Preview (Built-In, No Install)

Preview can merge PDFs, but the workflow isn't intuitive. Apple never added a "Merge" button — you have to use the thumbnail sidebar.

Step by step:

1. Open the first PDF in Preview.
2. Go to View → Thumbnails (or press ⌘⌥3) to show the page thumbnail sidebar on the left.
3. Click on the last page thumbnail in the sidebar to select it.
4. Now drag the second PDF file from Finder directly onto the thumbnail sidebar, dropping it below the last page thumbnail. You should see a green "+" icon and a horizontal line showing where the pages will be inserted.
5. The second PDF's pages appear in the sidebar. Repeat for additional files.
6. Go to File → Export as PDF to save the merged document.

Important: Use "Export as PDF," not "Save." If you use "Save," Preview overwrites the first file with the merged version — your original is gone.

Preview quirks:

• Drag positioning matters. If you drop the second file on top of a page thumbnail instead of between thumbnails, Preview replaces that page instead of inserting. This has caused many an accidental data loss.
• File size. Preview sometimes inflates the merged file. A merge of two 5 MB PDFs might produce a 15 MB file because Preview re-encodes images. If that happens, run the output through a PDF compressor.
• Bookmarks are lost. If your source PDFs have bookmarks (table of contents), Preview strips them during the merge.
• Form fields. Preview can merge PDFs with fillable form fields, but the form functionality sometimes breaks in the merged output.

Preview works well for quick, simple merges — combining two or three short documents. For anything more complex, use Method 2 or 3.

Method 2: Browser-Based Tool (Most Reliable)

If Preview's quirks frustrate you, or you need to merge more than 3–4 files at once, a browser tool is more reliable.

1. Open Safari or Chrome.
2. Go to whiskfile.com/tools/merge-pdf.
3. Click "Choose files" or drag all your PDFs onto the page at once.
4. Drag the thumbnails to reorder if needed.
5. Click Merge and download the result.

Advantages over Preview:

• Drag-and-drop reordering with visual thumbnails
• No risk of accidentally overwriting a source file
• Preserves bookmarks from source PDFs
• File size stays clean — no unexpected inflation
• Handles batch merges (10+ files) without issue
• Runs client-side in the browser — files don't upload to any server

Disadvantage: Requires a browser. But you already have one.

For most merge tasks, this is what I'd recommend. It's faster than navigating Preview's sidebar, and the results are more predictable.

Method 3: Automator (For Recurring Batch Merges)

If you regularly merge the same types of files — say, combining monthly reports into quarterly bundles — Automator can build a reusable workflow.

1. Open Automator (search for it in Spotlight).
2. Create a new Quick Action (or "Service" in older macOS).
3. Set "Workflow receives current" to PDF files in Finder.
4. Add the action "Combine PDF Pages" from the PDFs category.
5. Add "Move Finder Items" to specify where to save the merged output.
6. Save the workflow with a descriptive name like "Merge Selected PDFs."

To use it: Select multiple PDF files in Finder, right-click, choose Quick Actions → Merge Selected PDFs. The merged file appears in your chosen destination folder.

This is powerful for automation, but overkill for one-off merges. I only recommend this if you're merging PDFs at least weekly.

Common Problems and Fixes

"Preview crashes when I drag files into the sidebar"

This happens with large PDFs (50+ MB) or files with complex layer structures. Preview loads the entire document into memory for thumbnail rendering, and it can run out of RAM.

Fix: Close other applications to free memory, or use Method 2 which handles large files more efficiently.

"The merged PDF is way larger than the sum of the parts"

Preview re-encodes images during merges, sometimes at a higher quality than the original. A 3 MB + 4 MB merge producing a 12 MB file is a known Preview behavior.

Fix: Compress the merged PDF afterward. The compressor will optimize the re-encoded images back down, usually resulting in a final size close to or smaller than the sum of the originals.

"Pages are in the wrong order after merging"

In Preview, the drop position in the sidebar determines page order. If you drop above the wrong thumbnail, pages end up misplaced.

Fix: In Preview, you can drag individual page thumbnails to reorder them after merging. Or use the Organize PDF tool to visually reorder, then download.

"I need to merge PDFs with images (JPG, PNG)"

Preview only handles PDF files — you can't drag a JPG into the sidebar.

Fix: Convert your images to PDF first (the JPG to PDF tool does this), then merge. Or use the browser-based Merge PDF tool, which accepts both PDFs and images directly — no pre-conversion needed.

Which Method Should You Use?

| Scenario | Best Method | |---|---| | Quick merge of 2–3 small PDFs | Preview (Method 1) | | Merging 4+ files, or need bookmark preservation | Browser tool (Method 2) | | Merging mixed PDFs and images | Browser tool (Method 2) | | Recurring/weekly merge workflow | Automator (Method 3) | | Confidential documents, offline only | Preview (Method 1) or browser tool (client-side) |