Forgot to mention: the crash is caused by a received "Segmentation fault" signal:

Thread 1 "okular" received signal SIGSEGV, Segmentation fault.
0x00007fffd186ac67 in MediaRendition::copy() () from /usr/lib/x86_64-linux-gnu/libpoppler.so.58

After installing debug sybols for libpoppler I've got this backtrace:
Core dump: https://www.dropbox.com/s/y5synleuap2jb5t/core.7924?dl=0

#0  MediaRendition::copy (this=0x0) at Rendition.cc:390
#1  0x00007fffd1bb8e38 in Poppler::PageData::convertLinkActionToLink (a=0xc8d9f0, parentDoc=<optimized out>, linkArea=...) at poppler-page.cc:208
#2  0x00007fffd1bdc77f in Poppler::FormField::activationAction (this=this@entry=0xd519d0) at poppler-form.cc:149
#3  0x00007fffd1e41990 in PopplerFormFieldButton::PopplerFormFieldButton (this=0xd63480, field=0xd519d0) at /workspace/build/generators/poppler/formfields.cpp:36
#4  0x00007fffd1e3cc18 in PDFGenerator::addFormFields (this=this@entry=0xb8e840, popplerPage=popplerPage@entry=0xbc3470, page=page@entry=0xd50a50)
    at /workspace/build/generators/poppler/generator_pdf.cpp:1628
#5  0x00007fffd1e3dedd in PDFGenerator::loadPages (this=this@entry=0xb8e840, pagesVector=..., rotation=rotation@entry=0, clear=clear@entry=false)
    at /workspace/build/generators/poppler/generator_pdf.cpp:658
#6  0x00007fffd1e3e457 in PDFGenerator::init (this=this@entry=0xb8e840, pagesVector=..., password=...) at /workspace/build/generators/poppler/generator_pdf.cpp:583
#7  0x00007fffd1e3e603 in PDFGenerator::loadDocumentWithPassword (this=0xb8e840, filePath=..., pagesVector=..., password=...) at /workspace/build/generators/poppler/generator_pdf.cpp:538
#8  0x00007fffd6dc6961 in ?? () from /usr/lib/x86_64-linux-gnu/libOkular5Core.so.7
#9  0x00007fffd6dc6e34 in Okular::Document::openDocument(QString const&, QUrl const&, QMimeType const&, QString const&) () from /usr/lib/x86_64-linux-gnu/libOkular5Core.so.7
#10 0x00007fffd70d432e in Okular::Part::doOpenFile (this=this@entry=0x72a070, mimeA=..., fileNameToOpenA=..., isCompressedFile=isCompressedFile@entry=0x7fffffffd59f)
    at /workspace/build/part.cpp:1292
#11 0x00007fffd70d56e6 in Okular::Part::openFile (this=0x72a070) at /workspace/build/part.cpp:1414
#12 0x00007ffff7b97001 in ?? () from /usr/lib/x86_64-linux-gnu/libKF5Parts.so.5
#13 0x00007ffff7b97f0c in KParts::ReadOnlyPart::openUrl(QUrl const&) () from /usr/lib/x86_64-linux-gnu/libKF5Parts.so.5
#14 0x00007fffd70c79d9 in Okular::Part::openUrl (this=0x72a070, _url=...) at /workspace/build/part.cpp:1567
#15 0x00000000004127dc in Shell::openUrl (this=this@entry=0x731b10, url=..., serializedOptions=...) at /workspace/build/shell/shell.cpp:277
#16 0x00000000004150a6 in Shell::openDocument (this=this@entry=0x731b10, url=..., serializedOptions=...) at /workspace/build/shell/shell.cpp:218
#17 0x00000000004151d6 in Shell::openDocument (this=this@entry=0x731b10, url=..., serializedOptions=...) at /workspace/build/shell/shell.cpp:205
#18 0x000000000040c0bf in Okular::main (paths=..., serializedOptions=...) at /workspace/build/shell/okular_main.cpp:170
#19 0x000000000040bac3 in main (argc=2, argv=<optimized out>) at /workspace/build/shell/main.cpp:69

Can you please attach the file?

As I've said: this file cannot be published (it is a paid copy of magazine). Thus, I will send the file to you via mail privately.

Which poppler version are you using? seems ancient

Yep, I'd expect it to be ancient, since KDE Neon uses Ubuntu 16.04 LTS as its base.

I.e. the version (according to `apt info libpoppler58`) is: 0.41.0-0ubuntu1.2

Upgrading (lib)poppler to version 0.48.0-2ubuntu2.1 (from zesty/17.04) made the problem dissapear.

Built from here: https://packages.ubuntu.com/zesty/libpoppler-dev

Does this mean I should inform KDE Neon maintainers to update their poppler?

Yes, you could tell either them or Ubuntu that the software they ship is old and crashy.

A note of warning, updating libpoppler only may cause some weirdness in programs that use it directly (libreoffice pdfimport and some others), i'm even surprised you could update it, i would have guessed that apt would have complained