Why libreoffice hangs?

Hi LibreOffice world,

LibreOffice 5.1* getting hang while copying the contents of some .pdf file.
OS:Ubuntu 16.04.5 64Bit
Office:LibreOffice 10m0(Build:2)

I have solved this issue by “Copies the contents of that pdf file into normal text editor and than copy to libreoffice.Copying the Contents of pdf → normal text editor → copying the contents of normal text editor → LibreOffice”