When combining multiple pdf documents, it's been found that if those documents were batch-converted from docx to pdf through Windows Explorer right-click 'Convert to PDF' option, combined as sub-sections/parts/chapters, then combined together again to generate a complete document, that the final compiled pdf document will generate numerous font glitches in specific font types.

While the first-stage pdf conversions & combine-as-pdf (step-1&2) appear normal, when the resulting pdfs are combined into a single pdf file (step-3), the font glitches occur. This may manifest of dropped letters, unexplained spacing, odd formatting, or otherwise unintelligible text. We noticed this in our section headers in bold text.

We have not tested this across all documents, fonts, or MS Word styles, but have found it to be true across multiple versions of Acrobat for a recent specification set. Interestingly, it did not happen at all project stages, but was an on-going issue at the deliverables stage for unknown reasons.

Work-around: Print step-2 combined pdfs prior to combining into whole document.

Steps:
1. Batch-Convert (right-click) Style-formatted .docx files into single pdfs;
2. Combine pdfs into sub-sections (right-click or drag-drop)
3. Combine sub-sections into final unified pdf (right-click or drag-drop)

Acrobat DC
Win10-x64 Pro