Follow the steps in order to combine or merge multi pdf files into one:

1. Open one of your PDFs in Adobe Acrobat and click Combine Files on the right-side pane.
2. Drag and Drop files or click the Add Files button and navigate to select your files. Click Open when you’re done.
3. If you have all your files in a folder, click Add Files on the top bar and select Add Folder and select your folder. (Or select any of the other options if you find appropriate)
4. In the next screen you can see all your files that are selected. Click Add Files on the top bar if you want to add more files.
5. Click Combine when you’re satisfied with the files selected.
6. On the next screen you can review and edit your document. When you’re are satisfied click the File tab on the top left and select Save As.
7. Click Choose a Different Folder.
8. Navigate to where you want to save your document, name your document and click Save.

Follow the steps in order to add a signature to your pdf file:

1. Open a .pdf document on Adobe Reader.
2. Click on the Signature Button at the top menu.
3. Choose Add Signature or Add Initials depending on what you're looking for. The procedure to add both signature and initials are the same.
4. There are three different ways that you can add a signature or initial. By typing, drawing, or inserting an image.
   When in Type mode, simply start typing your signature or initials and it will show up in the box below.
5. You can also click on Change style on the right side to change the font.
6. In Draw mode, you can use your mouse to "draw" the signature if you want your signature to look more unique. Please note: Drawing with a mouse or trackpad might not be as accurate as writing your signature on paper.
7. Finally, you can take a picture of your signature on a white piece of paper and save it on your computer. Then in Image mode, navigate to the picture and select the picture of your signature and click Open. Now, you will be able to place that image on your pdf and use it as a signature.
8. After you are happy with your signature, click Apply at the bottom and your signature will be saved in Adobe and ready for use on your documents the next time after you click on the signature button.
9. Click on the signature that you wish to use. Your mouse pointer will become your signature. Click where you want your signature to be. After, you can resize the signature if needed. Click the Save button or File > Save As to save your signature in the document.