There are a lot of PDF files that you need to combine together as one PDF, what will you do? A PDF combiner is the first choice for you to combine PDF files to a single PDF.
Just enter 'PDF combiner' in Google or other search engine, you will find a long list of this kind of software. Which one is the best and easiest that suitable for your need? After comparing many PDF combiners, I find Simpo PDF Merge & Split, which not only supports to combine PDF files, but also can split a PDF to several PDFs. Here, I will take it as an example.
First, you can refer to detail introduction for the interface as below:
1. In this part, there are five buttons. You could import file(s) by "Add"; if you choose a file by mistake, don’t worry, only one click on "Remove", the file you don’t need is deleted; if you want to combine PDF files in another batch, "Clear" button will help you to delete all files before; as this PDF combiner will combine PDFs in sequence, if you want to change the position of a PDF, just click "Up" or "Down" for help.
2. If you click "Password", a pop-up box will open as below, 
this is used for entering user password if you select a PDF file protected by user password. "Merge Method" allows you to choose the way to combine PDFs, whole or part range.
3. You could set the output PDF name in this location.
4. Like all Simpo products, you can set the output path for your convenience.
5. "Advanced Setting" allows you to customize and secure your output PDFs.
6. Button to start PDF combine.
Now you can download this PDF combiner, and follow below steps to combine PDF files.
Step 1. Combine PDF files in a batch
After imported PDF files, it's time to combine PDF files. The default value for the merge method is "Whole", which means it will directly combine PDF files with the whole parts each. So, you just need click "Merge", then done!
Step 2. Combine PDFs with the specific parts
To combine PDFs with proper parts, you need to select that PDF file first, and then go to merge method. There are two options, whole and part, here, we should select "part", then type the range which you want to combine into a single PDF file. For each imported PDF files, you can make this selection.
Tips: PDF Merge & Split provides advanced feature for split as well. Please access to How to split a PDF file to see the detials.
