Closes #3983

Summary

This PR fixes an issue where newline characters were being incorrectly stripped from Table and TableChunk elements during PDF partitioning. The RE_MULTISPACE_INCLUDING_NEWLINES regex was being applied indiscriminately to all Text elements, including tables, which removed newlines that carry structural meaning (such as row separation).

Changes

• unstructured/partition/pdf.py: Added conditional logic to skip whitespace normalization for Table and TableChunk elements, preserving newlines that convey tabular structure
• CHANGELOG.md: Added entry documenting the fix
• unstructured/__version__.py: Version bump to 0.18.33

Problem

When processing PDFs (especially image-based PDFs with tables), the code applied this regex substitution to all Text elements:

el.text = re.sub(RE_MULTISPACE_INCLUDING_NEWLINES, " ", el.text or "").strip()

This stripped meaningful line breaks from table content, degrading the structural representation of tabular data.

Solution

Added a check to exclude Table and TableChunk elements from the whitespace normalization:

# Skip newline normalization for Table/TableChunk - newlines carry structural meaning
if not isinstance(el, (Table, TableChunk)):
    el.text = re.sub(
        RE_MULTISPACE_INCLUDING_NEWLINES,
        " ",
        el.text or "",
    ).strip()