this bug has been reported here:

https://bugs.edge.launchpad.net/ubuntu/+source/poppler/+bug/213852

"It crashed out overnight, I believe it was linked to the file indexing that the tracker program was doing at the time. As the only other thing that was still running was Transmission, since I was downloading a couple of torrent files."

".
Thread 1 (process 12665):
#0  Dict::lookup (this=0x7ffcf874c455, key=0x7ffcf8773c9c "Subtype", 
    obj=0x7fff00c1af30) at Dict.cc:61
No locals.
#1  0x00007ffcf86cde54 in FormField (this=0x62fa40, xrefA=0x62f340, 
    aobj=0x7fff00c1b0e0, aref=<value optimized out>, 
    aform=<value optimized out>, ty=<value optimized out>) at Object.h:259
No locals.
#2  0x00007ffcf86ce501 in FormFieldButton (this=0x7ffcf874c455, 
    xrefA=0x7ffcf8773c9c, aobj=0x7fff00c1af30, ref=@0x0, 
    form=0xfefefefefefefeff) at Form.cc:809
No locals.
#3  0x00007ffcf86cd4e0 in Form::createFieldFromDict (this=0x62eef0, 
    obj=0x7fff00c1b0e0, ptr=0x6321b0, xrefA=0x62f340, pref=@0x7fff00c1b100)
    at Form.cc:1155
	obj2 = {type = objName, {booln = 6498288, intg = 6498288, 
    real = 3.2105808575824223e-317, string = 0x6327f0, name = 0x6327f0 "Btn", 
    array = 0x6327f0, dict = 0x6327f0, stream = 0x6327f0, ref = {
      num = 6498288, gen = 0}, cmd = 0x6327f0 "Btn"}}
#4  0x00007ffcf86cdbb5 in FormField (this=0x62f9e0, xrefA=0x62f340, 
    aobj=0x7fff00c1b1e0, aref=<value optimized out>, 
    aform=<value optimized out>, ty=<value optimized out>) at Form.cc:700
No locals.
#5  0x00007ffcf86cd3ed in Form::createFieldFromDict (this=0x62eef0, 
    obj=0x7fff00c1b1e0, ptr=0x62fba0, xrefA=0x62f340, pref=@0x7fff00c1b1f0)
    at Form.cc:1163
	obj2 = {type = objNull, {booln = 12693968, intg = 12693968, 
    real = 6.9531442354212576e-310, string = 0x7fff00c1b1d0, 
    name = 0x7fff00c1b1d0 "\t", array = 0x7fff00c1b1d0, dict = 0x7fff00c1b1d0, 
    stream = 0x7fff00c1b1d0, ref = {num = 12693968, gen = 32767}, 
    cmd = 0x7fff00c1b1d0 "\t"}}
#6  0x00007ffcf86cd63d in Form (this=0x62eef0, xrefA=0x62f340, 
    acroForm=<value optimized out>) at Form.cc:1107
No locals.
#7  0x00007ffcf86c3b50 in Catalog (this=0x62f3e0, xrefA=<value optimized out>)
    at Catalog.cc:59
No locals.
#8  0x00007ffcf871d809 in PDFDoc::setup (this=0x62ef50, ownerPassword=0x0, 
    userPassword=0x0) at PDFDoc.cc:206
No locals.
#9  0x00007ffcf871d9ff in PDFDoc (this=0x62ef50, 
    fileNameA=<value optimized out>, ownerPassword=0x0, userPassword=0x0, 
    guiDataA=<value optimized out>) at PDFDoc.cc:102
No locals.
#10 0x0000000000401b0f in main (argc=3, argv=0x7fff00c1b4d8)
    at pdftotext.cc:152
	doc = (PDFDoc *) 0x62ef50
	fileName = (GooString *) 0x604010
	textFileName = <value optimized out>
	ownerPW = (GooString *) 0x0
	userPW = (GooString *) 0x0
	textOut = <value optimized out>
	f = <value optimized out>
	uMap = (UnicodeMap *) 0x62ed70
	info = {type = objNone, {booln = 4204389, intg = 4204389, 
    real = 2.0772441666528327e-317, string = 0x402765, 
    name = 0x402765 "H\205ít\0341Û\017\037@", array = 0x402765, 
    dict = 0x402765, stream = 0x402765, ref = {num = 4204389, gen = 0}, 
    cmd = 0x402765 "H\205ít\0341Û\017\037@"}}
	ok = <value optimized out>
	p = <value optimized out>
	exitCode = <value optimized out>"