Here's the page with just the flags and pennants extracted from the PDF, and also a Word doc in case you want to make up your own 'boat name' in flags and maybe print it out and laminate it so you can stick it on the bulkhead over the chart table.
I wonder how many people who know they have to fly the all-yellow letter-Q flag when coming into a new country that it's meaning comes form this code under
Q - My vessel is “healthy” and I request free pratique.
Interestingly, the code flags most often sighted as meaning 'splice the mainbrace' (as in previous link) are given as the UK code signals A, D, 2, 8.
Yet in fact, what appears in most cases I can find are the US flags for A, D, 2, 8. (as in previous link). See upper pic.
Which is probably not unusual on US-flagged vessels.
If the flags were older UK code flags, (see lower pic) I think the A-Alpha would look like the modern *International* Y-Yankee flag (alternate diagonal red yellow), the D-Delta would look like the International numeral 0-Zero (vertical red strip on yellow ground), 2 would be a pennant of red over blue (or black), with the 8 being an all red pennant.
The AD28 is indeed "Splice the Main Brace" - this is a Naval Signal with the 2 & 8 flags being naval numeric flags as opposed to numeral pennants used by civilians.
These signals used to be contained in Allied Tactical Publication 1 Volume 2 which was the signalman's bible back in my day as a bunting tosser with the grey funnel line..