fix PyPDF2 3.x page copying + rename documentation

- Added explicit page copying after cloneReaderDocumentRoot() calls
- Renamed PATCH_PDFWRITER.md to PATCH_PYPDF2_PDFWRITER.md
- Prevents 327-byte empty PDFs in PyPDF2 3.x

🤖 assisted by claude

odoo-bringout-oca-edi-pdf_helper/doc/PATCH_PYPDF2_PDFWRITER.md

@@ -0,0 +1,101 @@
+# PyPDF2 Compatibility Patch - PDF Helper (EDI)
+
+## Overview
+
+This package benefits from the PyPDF2 compatibility fixes implemented in the `oca-ocb-base` package. The pdf_helper module uses `OdooPdfFileWriter` and `OdooPdfFileReader` classes that are automatically compatible with PyPDF2 3.0.0+ through the main compatibility layer.
+
+## Problem
+
+In PyPDF2 3.0.0, several classes and methods were deprecated and removed:
+- `PdfFileWriter` → `PdfWriter`
+- `PdfFileReader` → `PdfReader`
+- Various method names changed (e.g., `addPage()` → `add_page()`)
+
+## Affected Functionality
+
+The pdf_helper module uses PyPDF2 indirectly through:
+- `OdooPdfFileWriter` for embedding XML attachments in PDFs
+- `OdooPdfFileReader` for extracting XML files from PDF documents
+- XML-to-PDF embedding for EDI workflows
+- PDF parsing and attachment processing
+
+## Solution
+
+**This package includes direct fixes** for PyPDF2 3.x page copying issue:
+1. Uses `OdooPdfFileWriter` from `odoo.tools.pdf` (oca-ocb-base) for compatibility
+2. **CRITICAL FIX**: Added explicit page copying after `cloneReaderDocumentRoot()`
+
+In PyPDF2 3.x, `cloneReaderDocumentRoot()` only copies document structure, not content pages. This was causing 327-byte empty PDFs. The fix includes explicit page copying:
+
+```python
+writer.cloneReaderDocumentRoot(reader)
+# Copy all pages from the reader to the writer (required for PyPDF2 3.x)
+for page_num in range(reader.getNumPages()):
+    page = reader.getPage(page_num)
+    writer.addPage(page)
+```
+
+## Files Using PyPDF2
+
+### `pdf_helper/utils.py`
+- Imports `PdfReadError` with compatibility handling
+- Uses `OdooPdfFileReader` (automatically compatible)
+
+### `pdf_helper/models/helper.py`  
+- Uses `OdooPdfFileWriter` and `OdooPdfFileReader` (automatically compatible)
+- **FIXED**: Added explicit page copying after `cloneReaderDocumentRoot()` and `addAttachment()`
+
+## Implementation Details
+
+**Direct code changes applied** in this package:
+
+1. **Dependency**: Requires `oca-ocb-base` with `pdfwrite` branch for compatibility classes
+2. **Page copying fix**: Added explicit page copying loops in multiple methods
+3. **Import handling**: Exception imports handle both old and new PyPDF2 locations
+
+## Testing
+
+The compatibility has been verified with:
+- PyPDF2 3.0.0+ (new API)
+- PyPDF2 2.x (old API)
+- XML embedding in PDFs
+- XML extraction from PDFs
+- EDI document processing workflows
+
+## Branch Information
+
+- **Branch**: `pdfwrite`
+- **Based on**: Current master branch
+- **Type**: Dependency compatibility (no direct patches)
+- **Impact**: Automatic compatibility through oca-ocb-base dependency
+
+## Dependencies
+
+**CRITICAL**: This package requires:
+- `oca-ocb-base` package on `pdfwrite` branch
+- The main PyPDF2 compatibility layer must be active
+
+## Author
+
+- **Developer**: Ernad Husremović (hernad@bring.out.ba)
+- **Company**: bring.out.doo Sarajevo
+- **Date**: 2025-09-02
+
+## Related Issues
+
+This documentation addresses PyPDF2 compatibility for:
+- EDI XML embedding workflows
+- PDF attachment processing
+- Electronic document interchange
+
+## Installation
+
+1. Ensure `oca-ocb-base` is using the `pdfwrite` branch
+2. Use this package's `pdfwrite` branch (for documentation compliance)
+3. No additional installation steps required
+
+## Future Considerations
+
+- Monitor oca-ocb-base compatibility updates
+- Test EDI workflows with future PyPDF2 versions
+- Consider direct PyPDF2 usage optimization if needed