user@ubuntu:/tmpfs$ convert PDFReference15_v6.pdf -page a4 pdfreferenceA4.pdf
Error: /ioerror in --showpage--
Operand stack:
   1   true
Execution stack:
   %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   false   1   %stopped_push   1862   1   3   %oparray_pop   1861   1   3   %oparray_pop   1845   1   3   %oparray_pop   --nostringval--   --nostringval--   1109   1   1172   --nostringval--   %for_pos_int_continue   --nostringval--   --nostringval--   1745   0   9   %oparray_pop   --nostringval--   --nostringval--
Dictionary stack:
   --dict:1159/1684(ro)(G)--   --dict:1/20(G)--   --dict:75/200(L)--   --dict:75/200(L)--   --dict:106/127(ro)(G)--   --dict:285/300(ro)(G)--   --dict:22/25(L)--   --dict:4/6(L)--   --dict:25/40(L)--
Current allocation mode is local
Last OS error: 27
GPL Ghostscript GPL Ghostscript 8.708.70: : Unrecoverable error, exit code 1
Unrecoverable error, exit code 1
convert: Postscript delegate failed `PDFReference15_v6.pdf': No such file or directory @ pdf.c/ReadPDFImage/612.
convert: missing an image filename `pdfreferenceA4.pdf' @ convert.c/ConvertImageCommand/2775.