Among the most popular PDF editors notes program from the developer of this format Adobe Acrobat. The app is a powerful tool which you can use to make almost any changes and saving documents. Install this program on your computer, downloading the installer from the Internet.
Run the program, using the tab "File" - "Create". Among the displayed options choose "Merge files into a single document." Then click on "Add files" and select to add documents.
Then in the program window to adjust the order of the joined files. For this you can use by dragging the item while holding the left mouse button. To remove page, click Remove. Using the menu items set up the display of the document.
After making entries, click "Combine files". Now, all attached documents are connected. Click "File" - "Save as" PDF. Ask a new file name, then press Save. The combine files is complete.
If you want to combine only two documents you can use special online services. So, you can use the resource of Free PDF Tools.
On the page select to merge the documents, then press "Merge" and wait for the end of the operation, which may take several minutes depending on the speed of your Internet connection. After that you will see on the page a link to download the new PDF file. Click on it and save the resulting file. Combining documents is completed.