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PDF MERGER & COMPRESSOR

COMBINE & COMPRESS PDFS AND IMAGES CLIENT-SIDE

Merge multiple PDF files and images into a single clean document with optional stream deduplication. All operations are processed 100% locally in your browser for absolute data privacy.

Queue & Settings

Drop PDF or image files here

Supports PDF, JPG, PNG, WEBP, BMP, TIFF

Compress PDF: Off

© 2026 Sezgin Karacaoglan (UnitedG) · PDF Merger & Compressor

All processing happens in your browser. Your files never leave your device.

COMPREHENSIVE MANUAL & ARCHITECTURE

HOW TO MERGE & COMPRESS PDFS LOCALLY

Learn how client-side WebAssembly and modern browser APIs allow you to combine documents and images without uploading sensitive data to external servers.

01 STEP-BY-STEP WORKFLOW

1. Queue Files

Drag and drop your PDF documents or raw image files (JPG, PNG, WEBP, BMP, TIFF) directly into the processing area, or click Browse Files to select them from your file manager.

2. Rearrange Order

Page assembly follows your precise queue structure. Grab any file item to drag it up or down to set the exact sequence before compilation begins.

3. Enable Compression

Switch on the Compress PDF toggle if you want the engine to eliminate redundant vector stream duplicates, remove invisible font descriptors, and strip lingering tracking metadata.

4. Compile & Save

Click Merge. The browser stitches all resources instantly into a standard compliant PDF. You will be prompted to select a destination directory or your download will initiate automatically.

02 ARCHITECTURAL HIGHLIGHTS & PRIVACY

100% Client-Side Execution

Unlike conventional online document tools that transmit your files to cloud processing clusters, UnitedG PDF Merger & Compressor executes every routine strictly in browser runtime memory via JavaScript typed arrays (Uint8Array) and the pdf-lib engine. At no point do your financial contracts, identity scans, or proprietary data traverse an external network.

Lossless Vector Stream Deduplication

When concatenating multiple digital documents (such as invoices or presentations), repeated vector branding, corporate fonts, and layout elements often create unnecessary bloat. Our compression routine enumerates all indirect PDF objects, applies a lightweight 32-bit hash on raw streams, and deduplicates identical object references across the document catalog, drastically reducing storage weight without downsampling textual sharpness.

Native Image Canvas Normalization

Imported images (including WebP, BMP, and TIFF) that lack native PDF dictionary mappings are automatically drawn onto an in-memory virtual HTML5 canvas context. They are rendered to standard ISO A4 aspect dimensions while preserving native pixel ratios, ensuring uniform margins and crystal-clear print legibility.

03 FREQUENTLY ASKED QUESTIONS

Are my uploaded documents stored on UnitedG servers? +

No. There are no server uploads whatsoever. The entire reading, merging, optimizing, and binary compilation pipeline runs exclusively inside your browser's local sandbox memory. Once you close or reload the browser tab, all cached memory buffers are instantly purged.

What file formats can I merge into a single PDF? +

You can seamlessly mix and combine standard Adobe PDF files (.pdf) alongside raster and modern web image formats, including JPEG (.jpg, .jpeg), PNG (.png), WebP (.webp), Bitmap (.bmp), and TIFF (.tiff, .tif).

Can I process password-protected PDF files? +

Encrypted documents requiring an owner or user password cannot be merged directly due to browser security restrictions. Please decrypt or print the protected PDF to an unlocked file before loading it into the merge queue.

Does the compression toggle degrade image quality? +

The primary compression engine operates losslessly. It focuses on removing catalog metadata trees, unused structure elements, and duplicate font descriptors. High-resolution photos retain their original fidelity unless canvas normalization is required for unsupported raster formats.

IN-DEPTH ARCHITECTURE & COMPLIANCE

CLIENT-SIDE PDF ENGINEERING & DATA PRIVACY

A technical breakdown of in-memory binary compilation, client-side deduplication mechanics, and why zero-upload architecture is essential for modern data protection standards.

04 CLIENT-SIDE MEMORY VS. TRADITIONAL CLOUD CONVERTERS

Zero Data Ingestion & Network Air-Gapping

Standard cloud-based PDF aggregators require users to upload documents to a remote server cluster where files are staged, deserialized, stitched together, and temporarily retained in server-side storage queues. Even if vendors advertise automated hourly deletion, every upload represents an active data transfer across the public web. This introduces systemic vulnerabilities, including man-in-the-middle risks, unauthorized third-party caching, and jurisdictional compliance violations under regulations such as GDPR (General Data Protection Regulation) or HIPAA.

Sandboxed V8 Execution via Uint8Array Memory Buffers

UnitedG PDF Merger & Compressor replaces cloud processing pipelines by utilizing the browser's native JavaScript virtual machine (e.g., Google Chrome's V8 or Mozilla's SpiderMonkey). Incoming streams are read directly from local storage using the HTML5 FileReader API and mounted directly into volatile ArrayBuffer and Uint8Array allocations. Computation runs entirely isolated inside the current active browser tab; no networking sockets or telemetry endpoints are called.

05 PRODUCTION WORKFLOWS & COMMON SCENARIOS

Job Applications & Resumes

Consolidate your cover letter, resume, work certificates, and reference scans (PNG/JPG) into a single, cohesive PDF portfolio with standardized page dimensions and zero layout shifting.

Tax Documents & Financial Audits

Assemble monthly expense statements, bank receipts, and scanned invoices into one audit-ready package. Local in-memory processing guarantees that banking data remains confidential.

Legal Contracts & Scans

Stitch together multi-page signed agreements with photo attachments. Lossless deduplication strips duplicated corporate letterhead graphics to keep files within email attachment limits.

Creative Portfolios & Artwork

Combine high-resolution WebP or TIFF concept renderings alongside text descriptions. Canvas normalization centers images cleanly onto an A4 document grid without stretching.

06 HOW THE MULTI-LAYER COMPRESSION PIPELINE OPERATES

1. Structural Catalog Sanitization

PDF documents created across modern design suites frequently embed invisible diagnostic data: editing application histories, XML metadata packages (XMP), thumbnail previews (Thumb), and structural tree elements (StructTreeRoot). Our compression engine deletes these unused references directly from the PDF dictionary without affecting vector lines, font curves, or embedded bitmaps.

2. Stream Hashing & Indirect Object Deduplication

When merging multiple documents that share identical assets—such as company logos, background shapes, or font sub-dictionaries—the resulting file typically balloons in size. The compressor applies an internal 32-bit fast-hash algorithm across all indirect stream objects. Duplicate objects are mapped to the primary reference (PDFRef), while the redundant byte sequences are permanently unlinked and garbage-collected.

3. Binary Object Stream Packaging (Cross-Reference Streams)

During final binary serialization, output streams are written with useObjectStreams: true enabled. Instead of maintaining verbose ASCII cross-reference tables, multiple indirect objects are compressed inside dense binary object streams, maximizing storage efficiency for fast opening and rendering.

07 TROUBLESHOOTING & TECHNICAL SPECIFICATIONS

Is there a maximum file size or page limit when merging documents? +

Because processing runs locally inside your browser, the only constraint is your computer's available RAM. Modern 64-bit browsers can effortlessly assemble hundreds of pages or several gigabytes of raw data. For optimal performance on standard office hardware, keeping batches under 200–300 MB ensures instantaneous compilation without tab freezing.

Will embedded vector paths or text layers be converted into flat images? +

No. Native PDF text objects, vector graphics, form fields, and true font curves remain 100% vector-based and fully searchable. The engine only invokes HTML5 canvas normalization for raw external image formats (such as WebP or TIFF) that do not natively map to standard PDF color spaces.

Does this tool work completely offline without an internet connection? +

Yes. Once the web application and supporting library scripts (like pdf-lib) have finished caching in your browser, you can disconnect your network connection entirely. You can merge, reorder, compress, and save files in an air-gapped environment.

How does UnitedG ensure compliance with GDPR (DSGVO) and privacy regulations? +

Under GDPR, transmitting personal or corporate information requires clear legal basis, data processing agreements (DPA), and explicit consent. Because UnitedG never ingests, transmits, logs, or stores your input files, no personal data processing takes place on remote servers, fulfilling the strict principle of Privacy by Design.