I've tried the trimbox, but it is still wanting to print to Letter. When looking at the pdf file in notepad, I'm not seeing any reference to the word "Legal", or "Letter" either for that matter. Here's the header in the file:
%PDF-1.4
%Çìó¢
1 0 obj << /Type /Catalog /ViewerPreferences << /NonFullScreenPageMode
+ /UseNone >> /PageLayout /SinglePage /Pages 2 0 R /PageMode /UseNone
+>> endobj
2 0 obj << /Type /Pages /Kids [ 5 0 R ] /Resources 3 0 R /Count 1 >> e
+ndobj
3 0 obj << /ProcSet [ /PDF /Text /ImageB /ImageC /ImageI ] >> endobj
4 0 obj << /Producer (PDF::API2 2.019 [linux]) >> endobj
5 0 obj << /Type /Page /Contents [ 10 0 R ] /MediaBox [ 0 0 612 1008 ]
+ /Parent 2 0 R /Resources << /Font << /PaLiCBB~1313689461 6 0 R >> /P
+rocSet [ /PDF /Text /ImageB /ImageC /ImageI ] >> /TrimBox [ 0 0 612 1
+008 ] >> endobj
6 0 obj << /Type /Font /Subtype /Type0 /DescendantFonts [ 7 0 R ] /Enc
+oding /Identity-H /BaseFont /PalatinoLinotype /Name /PaLiCBB~13136894
+61 >> endobj
7 0 obj << /Type /Font /Subtype /CIDFontType2 /W [ 0 [ 535 ] 4 [ 610 ]
+ 11 [ 336 333 726 ] 15 [ 945 ] 18 [ 604 ] 20 [ 667 524 ] 138 [ 500 ]
+140 [ 443 610 479 333 ] 145 [ 582 291 ] 148 [ 556 ] 151 [ 582 545 ] 1
+55 [ 395 423 326 ] 160 [ 833 ] 342 [ 500 500 ] 346 [ 500 ] 348 [ 500
+500 500 ] 496 [ 250 ] 550 [ 320 ] 556 [ 333 ] 561 [ 250 ] ] /BaseFont
+ /PalatinoLinotype /CIDSystemInfo << /Supplement 0 /Ordering (Identit
+y) /Registry (Adobe) >> /CIDToGIDMap /Identity /DW 1396 /FontDescript
+or 8 0 R >> endobj
8 0 obj << /Type /FontDescriptor /Ascent 731 /Flags 42 /AvgWidth 524 /
+Descent -284 /FontWeight 400 /StemV 0 /CapHeight 839 /FontFamily (Pal
+atinoLinotype) /FontName /PalatinoLinotype /MaxWidth 1396 /FontStretc
+h /Normal /Style << /Panose <010402040502050505030304> >> /ItalicAngl
+e 0 /StemH 0 /XHeight 419 /FontBBox [ -169 -291 1419 1049 ] /FontFile
+2 9 0 R /MissingWidth 1396 >> endobj
9 0 obj << /Length1 48568 /Filter [ /FlateDecode ] /Length 11 0 R >> s
+tream
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