A submission pack may need a cover sheet, selected pages of a report and a separate diagram in one PDF. Combining everything indiscriminately can include internal notes or duplicate attachments. Start with a page list that describes the pack you intend to deliver.

In Preview on Mac, changes can save automatically. Duplicate the PDFs before assembling the pack, and give the working destination a recognisable name. Keep the originals in their original folder so a change to the pack cannot be confused with a revised source report.

Build the intended page sequence

Open the working PDFs and choose View, Thumbnails in each window. Select the required thumbnails in the source copy; Command-click can select non-adjacent pages. Drag them into the destination sidebar at the intended insertion point. Drag destination thumbnails to adjust their order.

Use a small insertion first. If a cover has one page and the report begins immediately after it, confirm that the first report page is now second. This boundary check is more reliable than judging the pack by its total page count alone.

When adding a whole PDF, Apple also supports dragging its Finder icon into the destination sidebar. Do this only when every page belongs in the deliverable. A complete attachment and a selected extract are different editorial decisions.

Inspect the assembled document

Save the pack under its delivery name, close it and reopen it. Compare the page sequence with your list. Read the first and last page of each inserted section, check orientation and ensure a diagram has not been omitted because its thumbnail looked blank.

Check any contents page or written page references after assembly. The visible page position may have changed even though a printed page number inside the source remains the same.

Keep the page list and source files until the pack is accepted. If one source changes later, rebuild the affected section deliberately and repeat the boundary checks rather than appending a second version without removing the superseded pages.

References: Apple: combining PDFs in Preview.