I opened existing job but some text showed junk characters even though all fonts are installed.

[ModeratorPI]

Some fonts combine with their bold version to form a pair of that font. If these fonts are not installed in pair then the text which is having such font if we try to make it as bold by selecting the bold option, the text which appeared is not readable. To overcome this problem you need to install fonts in Pair.
For example, 709 will be get installed as bold of 708. But at this time in font list you will get only 708 and 708 Bold can not be seen. 708 and 709 are appeared as two individual fonts. So by selecting this option, you can install fonts in Pair.