How to Merge, Split, and Convert PDF Files Online

PDF (Portable Document Format) was created by Adobe in 1993 with a simple goal: allow documents to look exactly the same on any device or operating system. Three decades later, PDF has become the universal standard for contracts, reports, invoices, academic papers, and official documents of all kinds. But many people use PDFs without knowing the best tools and techniques for working with them. This guide covers the most common PDF operations and when to use each.

PDF Merge: Combining Multiple Files

Merging PDFs combines two or more PDF files into a single document, maintaining the page order of each input file. This is one of the most common PDF operations, used for:

Combining a cover letter and resume — Employers and recruiters often request documents as a single PDF. Merge your cover letter, resume, and portfolio into one file.
Assembling reports — Combine charts, data tables, and written analysis from different sources into a single coherent document.
Contract packages — Merge the main contract with exhibits, addenda, and signature pages for a complete, ordered document package.
Invoice batching — Combine monthly invoices into a single PDF for filing or submission to accounting departments.
Scanned document consolidation — When scanning multi-page documents one page at a time, merge the individual page PDFs into a complete document.

Order matters. Most PDF merge tools let you reorder files before merging. Always preview the final page order before downloading.

PDF Split: Breaking Files Apart

Splitting a PDF extracts pages or page ranges from a larger document into separate smaller files. Common use cases:

Extracting specific pages — Pull a single contract clause, a particular chart, or specific pages for sharing without sending the full document.
Dividing a scanned archive — Large multi-document scans (a box of files scanned as one PDF) can be split into individual document files.
Separating chapters — Break a long report or thesis into individual chapter PDFs for easier navigation and sharing.
Creating handouts — Extract specific slides or pages from a presentation PDF for distribution.

Most split tools allow three modes: split by page range (pages 1-10, 11-20, etc.), split every N pages (one file per page, or one per 5 pages), or extract specific individual pages.

PDF Compression

PDF files containing images — particularly high-resolution photos or scanned documents — can become very large. PDF compression reduces file size by:

Reducing the resolution of embedded images (downsampling)
Re-compressing images with higher JPEG compression
Removing embedded fonts that are not needed
Stripping metadata and embedded thumbnails

Compression is ideal for: emailing large documents (many email systems limit attachments to 10-25MB), uploading to web forms with file size limits, and archiving documents where storage space matters.

Trade-off: Aggressive compression reduces image quality. For documents where visual fidelity matters (photography, high-detail technical drawings), use moderate compression and verify the output quality before distribution.

PDF Conversion

Converting between PDF and other formats is a frequent need:

PDF to Word (.docx) — Converts PDF text and layout to an editable Word document. Works best on text-based PDFs with simple layouts. Scanned PDFs (images of text) require OCR (Optical Character Recognition) and may produce imperfect results.
Word/Excel to PDF — Convert Microsoft Office documents to PDF for universal compatibility and to prevent formatting changes when the recipient opens the file.
Image to PDF — Convert JPG, PNG, or other image files to PDF for standardized sharing and printing.
PDF to images — Extract pages as high-resolution PNG or JPEG files for use in presentations, web pages, or further editing.

Privacy When Working with PDFs

PDFs often contain sensitive information — contracts, medical records, financial documents, personal identification. Before using any online PDF tool, understand how they handle your files:

Client-side processing — The gold standard. Your files are processed in your browser and never leave your device. No server upload means no data exposure.
Server-side with deletion policy — Many tools upload files to servers but delete them immediately after processing (often within minutes or hours). Check the privacy policy for explicit guarantees.
Unencrypted transfer — Always verify that the tool uses HTTPS. Files uploaded over HTTP can be intercepted.

For highly confidential documents (legal contracts, medical records, financial statements), use locally-installed software or tools with explicit client-side processing guarantees.

PDF Metadata

PDFs can contain extensive metadata: author name, creation date, modification date, software used to create it, and even revision history. Before sharing PDFs externally, consider whether this metadata is appropriate to share. Most PDF tools include options to strip metadata from files.

Summary

The main PDF operations — merge, split, compress, and convert — cover the vast majority of real-world PDF workflows. Merging combines files in order; splitting extracts specific pages; compression reduces file size with some quality trade-off; and conversion enables editing or reformatting. For sensitive documents, always verify how the tool handles your files and whether processing is client-side or server-side.