The print options that you set for a file in FileMaker Pro have no effect on the print options for the same file in FileMaker Go, and vice versa. See printing : FileMaker Go 16 Development Guide
Appending PDF is not supported in FMGo. Under Notes : FileMaker Pro 16 Help
To answer your question
I haven't tried yet but I believe you need a landscape layout, then when you save as pdf it will remain in landscape. In FMGo you need two different layouts, Portrait and Landscape because it can't be changed in FMGo.
I have added another layout, specifically in iPad landscape mode, with all items copied and pasted from the original and that seems to be working correctly, although for some reason, the original layout is now exporting in landscape as well .
I guess my 1kb pdf changing into a 500 kb pdf was the file being overwritten rather than appended to.
I've found that PDF files print best when you define the layout type, landscape or portrait, and create the layout size to match. Use the Show Margins options and set the boundaries accordingly. Show Margins will not display if the Navigator is showing on the layout which is not a problem since that isn't part of a pdf.
Note: Have you tried enlarging the Header to full page to create a cover? Sadly this won't work with the footer.
I believe it was being overwritten.
I just got done testing myself on my iPhone with landscape. I will create another test with both portrait and landscape.
The documentation is not real clear. I created two scripts. Both use the Print Setup step with dialog turned off. I have one script for Portrait, then another for Landscape. It worked with the test from my iPhone. I used the same layout for both, just different scripts. Here is my test file : Dropbox - iOSLandScape.fmp12
When doing a test with various conditions, it's helplful as in this case to name files:
This way they will only overwrite themself and you will see what you hope to get by the name.
You can change the name after debugged...
I can look at the PDF and tell which is landscape and which is portrait. No need to rename my file.
The OP didn't know that append to PDF is not supported in ios. His original statement was that "Append PDF" fixed his issue, or at least appear too. I was stating instead of appending, it may have been over writing.
Of course one can open a pdf and tell if portions are landscape or portrait...
My suggestion was intended as a method to determine what was happening in the original question. At least I thought it was.
He used the same name because he wanted to append to the original file, because the op did not know append was not supported on ios devices. When you append to a pdf you have to use the same filename.
I did the same.... Rats....