## `qpdf`
- **Summary**: A powerful command-line program that performs transformations on PDF files.
- **Projects**: Encrypting, decrypting, merging, splitting, and compressing PDF files; modifying PDF metadata.
- **Commands**:
  - Encrypt: `qpdf --encrypt user-password owner-password 128 -- input.pdf encrypted.pdf`
  - Decrypt: `qpdf --password=your-password --decrypt encrypted.pdf decrypted.pdf`
  - Merge: `qpdf --empty --pages file1.pdf file2.pdf -- output.pdf`
  - Split: `qpdf input.pdf --split-pages=output_`
  - Compress: `qpdf --stream-data=compress input.pdf compressed.pdf`

## `fix-qdf`
- **Summary**: Repairs or normalizes QDF files (a special type of PDF file used for editing).
- **Projects**: Repairing QDF files that have become corrupted or are not functioning correctly.
- **Command**: `fix-qdf input.qdf output.pdf`

## `qpdfview`
- **Summary**: A tabbed PDF viewer using the Poppler library.
- **Projects**: Viewing multiple PDFs simultaneously in a tabbed interface; useful for comparing documents or multitasking.
- **Command**: `qpdfview input.pdf`

## `zlib-flate`
- **Summary**: A command-line tool to compress or decompress data using zlib.
- **Projects**: Compressing or decompressing streams within PDF files.
- **Command**:
  - Compress: `echo "Hello" | zlib-flate -compress > compressed.fl`
  - Decompress: `zlib-flate -uncompress < compressed.fl`

## `pdftopdf`
- **Summary**: A PDF conversion and manipulation tool, often used for preparing PDFs for printing.
- **Projects**: Optimizing PDF files for printing, such as booklet printing or page scaling.
- **Command**: `pdftopdf --booklet true input.pdf output.pdf`

## `pdfdetach`
- **Summary**: Extracts embedded files (attachments) from a PDF.
- **Projects**: Retrieving embedded files from PDF documents for separate analysis or use.
- **Command**: `pdfdetach -saveall input.pdf`

## `pdfattach`
- **Summary**: Attaches files to a PDF.
- **Projects**: Adding supplementary files or data to a PDF document.
- **Command**: `pdfattach --attach-file data.txt input.pdf output.pdf`

## `pdfgrep`
- **Summary**: Searches text in PDF files, similar to the Unix `grep` command.
- **Projects**: Finding specific text in large PDF documents or across multiple PDF files.
- **Command**: `pdfgrep "search term" input.pdf`

## `pdfseparate`
- **Summary**: Extracts individual pages from a PDF.
- **Projects**: Creating separate PDFs for each page of a document, useful for distributing individual pages.
- **Command**: `pdfseparate input.pdf output_%d.pdf`

## `pdfunite`
- **Summary**: Merges several PDF files into one.
- **Projects**: Combining multiple PDF documents into a single file.
- **Command**: `pdfunite input1.pdf input2.pdf output.pdf`

## `pdftocairo`
- **Summary**: Converts PDFs to other file formats like PNG, JPEG, PS, EPS, SVG.
- **Projects**: Converting PDF pages to images for use in web development, graphics design, or presentations.
- **Command**: `pdftocairo -png input.pdf output`