You can combine several PDF files into one. Click Merge PDF on the Tools tab. A new window will open. Click Add Files to add the PDFs that you want to merge and then click Merge. The original document will not be altered.

You can rearrange the selected files by clicking Move Up and Move Down. To remove a file you already added, click Remove.

You can also take just certain pages from the input files. To do this, add a file and then click inside the Select Range column to select the pages to use.

You can use the built-in PDF viewer to navigate in the PDF.