Recently I updated my lubuntu version from 16.04 to 18.04 and since then I have had issues displaying certain symbols pdf plots (using evince). The pdf file I am trying to display is the following:
https://www.dropbox.com/s/mc2wp2y8q2af1vj/stupidPlot.pdf?dl=0
On my screen it appears as in the following screenshot:
while it should appear as follows:
So the greek symbols delta, gamma and capital delta are not displayed as expected. After some searching I suppose it must be related to the fact that the fonts are not embedded in the pdf file I am trying to read (though I am not sure, so correct me if this is not the case). pdffonts gives the following output:
name type encoding emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
Times-Italic Type 1 WinAnsi no no no 7 0
Times-Bold Type 1 WinAnsi no no no 8 0
Times-BoldItalic Type 1 WinAnsi no no no 9 0
Helvetica Type 1 WinAnsi no no no 10 0
Helvetica-Oblique Type 1 WinAnsi no no no 11 0
Helvetica-Bold Type 1 WinAnsi no no no 12 0
Helvetica-BoldOblique Type 1 WinAnsi no no no 13 0
Courier Type 1 WinAnsi no no no 14 0
Courier-Oblique Type 1 WinAnsi no no no 15 0
Courier-Bold Type 1 WinAnsi no no no 16 0
Courier-BoldOblique Type 1 WinAnsi no no no 17 0
Symbol Type 1 Symbol no no no 18 0
Times-Roman Type 1 WinAnsi no no no 19 0
ZapfDingbats Type 1 ZapfDingbats no no no 20 0
Symbol Type 1 Symbol no no no 21 0
I tried to fix it using the suggestion given on:
https://stackoverflow.com/questions/10277418/the-pdf-viewer-evince-on-linux-can-not-display-some-math-symbols-correctly to run GhostScript as follows:
gs -o gs-repaired—stupidPlot.pdf -dPDFSETTINGS=/prepress -sDEVICE=pdfwrite stupidPlot.pdf
which does not seem to work and gives the error:
**** Error: Encountered 'obj' while expecting 'endobj'.
Treating this as a missing 'endobj', output may be incorrect.
**** Error: Encountered 'obj' while expecting 'endobj'.
Treating this as a missing 'endobj', output may be incorrect.
Processing pages 1 through 1.
Page 1
Loading NimbusSans-Regular font from /usr/share/ghostscript/9.26/Resource/Font/NimbusSans-Regular... 5086732 3571608 2679472 1286852 4 done.
Loading StandardSymbolsPS font from /usr/share/ghostscript/9.26/Resource/Font/StandardSymbolsPS... 5119500 3664456 2699672 1302649 4 done.
**** This file had errors that were repaired or ignored.
**** Please notify the author of the software that produced this
**** file that it does not conform to Adobe's published PDF
**** specification.
**** The rendered output from this file may be incorrect.
Moreover I have to produce many (tens of) thousands of pdf plots, so it would be preferable not to have to embed fonts in them in order to display them correctly.
So I wonder if anyone knows what might have changed when updating from lubuntu 16.04 to 18.04 (in 16.04 the plots were always correctly displayed), and how I could correctly display the pdf's in evince, preferably without having to embed the fonts in the pdf.
I also tried using xpdf and okular as alternatives to evince, but they displayed the symbols wrongly in the same manner.
Best Answer
Opening the file in Adobe Illustrator you'll find out that the glyph font is actually https://en.wikipedia.org/wiki/Symbol_(typeface) It likely comes with e.g. Adobe Reader, but not with evince. At the same time you probably don't have the font installed as system font, so there is nothing to fall back to. Props to envince for not silently substituting it with other font.
Last thing that could make this display correctly is if the font was embedded at creation with the file (full info within the pdf itself). However based on https://root-forum.cern.ch/t/embed-fonts-in-pdf/21666/2 ROOT does not allow to embed fonts to keep the file size small.
tl;dr Make sure the font is set to "Helvetica" which unless on mac will give you Arial, but either way you should be able to display the symbols correctly then.