The list in the center of the dialog shows files, that will be combined to form a new PDF document. You can add each file several times. The files will be combined in the order, in which they are listed. You can use appropriate buttons from 'Sort list' groupbox to sort the list. You can add files to the list, add all files from specified directory to the list, remove selected item from the list ( to do so use corresponding buttons from 'Manage list' groupbox).
For each file you can specify pages to be added (all pages, selected range, selected pages).
Range should be specified in the following way (for example):
1-3 or 3-1 (order matters!), 3-end etc.
Selected pages should be specified in the following way (for example):
1 3 5 3 2 6 7 - pages may repeat, order matters.
Rotation: pdftk can rotate pages (documents). Click help button to get short information about available options. For more detailed one, please refer to pdftk help.
Qualifier: pdftk can add only odd (even) pages from selected page range.
Encryption: you can encrypt output file with owner password. (from version 0.1.9 - also with user password)