You can split and merge documents from the Unsorted folder under Documents tab within appropriate transactions and assign them to the required task of the checklist. In order to do this please select the document that you wish to split/merge and find the Edit button on the right-hand side of the screen.
For merging documents, please select the document that you wish to merge, choose the "Merge with" option from the list, select one by one all other documents you want to merge with the current one by clicking the add document link, and type the merged document name. Once you click on the Merge button, you will find the merged document on the top of your Unsorted document's list.
For splitting the document, please select the document that you wish to split, choose the "Split" option from the list, enter the required pages, where "From" will be the first page of the new document, and "To" - the last page. You can select the appropriate document name from the drop-down list, which will automatically assign it to the Checklist task once you hit the Split button or enter the name of the document, which will save it under the Unsorted folder.
Please view the video below for details.