You can merge multiple PDF files into one document if, for instance, your scanner produced individual pages of a document while scanning, or you have multiple documents that would just work better as a single file. Take advantage of the Combine Files tool in Adobe Acrobat XI to merge existing PDF files. If you don't have a copy of Acrobat, you can merge PDF files online for free using PDFMerge and Merge PDF.
Merging Using Adobe Acrobat
Click "File" on the main menu in Adobe Acrobat XI, select "Create" and then click "Combine Files into a Single PDF" to launch the Combine Files dialog.
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Click "Add Files" and select the files you want to merge. Once you've added the files, drag and drop them in the order you want them to appear in the final, merged document.
Click "Combine Files" to combine the files in the specified order.
Click "File" on the main menu in Acrobat, select "Save As" and then select "PDF." Enter an identifying name for your merged file and click "Save."
Using the PDFMerge Website
Visit the PDFMerge website (link in Resources).
Click the "Choose File" button and select the first PDF file you want to merge. Repeat this step for each PDF file to include in the final merged document. Add files in the order you want them to appear.
Click the "Merge" button to merge the files into one PDF document. The merged document is automatically downloaded to your computer when the merge process is complete.
Using the Merge PDF Website
Visit the Merge PDF website (link in Resources).
Drag and drop a PDF file from your computer onto the "Drop PDF(s) here" box on the Merge PDF website. Alternatively, click the "Choose File" button and manually select files using a standard file upload dialog.
Click the "Add more PDFs" icon and add another PDF file. Repeat this step for each subsequent PDF file you want to merge into the final document.
Drag and drop the PDF file icons to place the documents in the order you want them to appear in the final merged PDF.
Click "Merge PDF" to merge the documents. When the process completes, click "Download File Now" to save the merged file to your computer. If you want to save the merged PDF on Dropbox or Google Drive, click the respective icons located at the right end of the Download File Now button.