You can use our 'Merge PDFs' automation for this.

Select the PDF Attachment Fields that contain the source files. You can select as many fields as you wish. Arrange the fields in the order in which their PDFs should be merged. Then select the Merged PDF Field where the combined file should be saved and run the automation.

Some PDFs restrict editing or copying but still open without a password. When these pages cannot be merged directly, miniExtensions can turn each page into an image and add it to the merged PDF. With this method, text becomes part of the page image, so you can no longer select or search it as text.

There is no setting to enter a PDF password. If a file needs a password to open, use a copy you have permission to use that opens without a password. Check the merged file before sharing it.